MBT301 Final Exam

Proteinaceous compounds

Lipids can include triglycerides, phospholipids, fatty acids, and sterols. Large proteins Peptides

Cocoa fermentation initially involves a(n)

Alcoholic fermentation

Specialty mushroom Lentinula edodes is grown on

All of the above (Logs of oak, Logs of Shi, Synthetic logs)

The fermentative activities of Gram-positive micrococci are particularly important in the production and preservation of a wide range of meat sausages. The biological stabilization is achieved usually through the addition of salts and the generation of lactic acid by

All of the above (Pediococcus cerevisiae, Lactobacillus plantarum, Staphylococcus carnosus)

Single cell protein is

All of the above (Whole cells of microorganisms, Carbohydrates and lipids, Nucleic acids, mineral salts and vitamins)

At the farm site pathogenic bacteria that can contaminate milk are introduced via

All of the above (Wild animals and farm environment, Water and environment, Farm workers and equipment/holding tanks)

Exploitation of fruiting fungi for the generation of edible biomass has which of the below advantages

All of the above (easy harvesting of fruiting bodies to separate edible biomass from the substrate in solid state fermentation, superior protein conversion efficiency per unit of land and per unit of time compared with animal sources of protein and most efficient conversion of plant waste into edible food, directly edible delicacies because of their texture and flavor unlike other single cell proteins)

Microbial serine proteinases used in cheese ripening are produced by

Aspergillus

Miso is a type of condiment essential to Japanese cuisine which is made from ingredients such as soy beans or rice fermented by adding a fungus called

Koji

Soy sauce fermentation involves which of the below basic stages

Koji, Moromi and Alcoholic fermentation

Heterolactic

Many bacteria perform heterolactic fermentation, producing a mixture of lactic acid, ethanol and/or acetic acid, and CO2 as a result, because of their use of the branched pentose phosphate pathway instead of the EMP pathway for glycolysis.

During butter fermentation diacetyl that has a buttery/butterscotch character is produced by

Yeast

Two naturally present antimicrobials in milk are

Agglutinins and Lactoperoxidase-isothiocynate system

Fermented dairy products are

All of the above (Cheeses, yogurt, buttermilk, Dahi, kumiss, kefir, Sour cream and acidophilus milk)

Black truffle is the fruiting body of

Tuber melanosporum

Penicillin is produced by a

fed-batch fermentation

Penicillin recovery after fermentation follows removal of mycelium using

rotary vacuum filters

Microbial enzymes are predominantly produced by

submerged fermentations

Ultra pasteurized milk involves heat treatment at

280°C for 3secs

What is the current number of functional food ingredients that are produced by microbial processes?

30

Dialysis is a process of separating molecules in solution by

differences in their rates of diffusion through a semi-permeable membrane

Fermentation conditions favouring rapid growth rates and high protein content during single cell protein production can also promote elevated RNA levels. This can be problematic as the digestion of nucleic acids by humans and animals can lead to the generation of purine compounds resulting in the

elevated plasma levels of uric acid

Species of the filamentous fungus Claviceps, which are pathogens of grasses, produce a range of alkaloids. Some of the best-known ones are

ergots

Butter is a dairy product made by churning

fresh or fermented cream or milk

Propionic acid and its salts are used in food as

fungistatic agent

Certain fermentation media nutrients or environmental conditions may affect not only the physiology and biochemistry, but also

morphology of the microorganism

Sourdough is a bread product made by a long fermentation of dough using

naturally occurring streptococci and yeast

Alkaloids, are produced by certain plants and microorganisms and they are a diverse group of small

nitrogen containing organic compounds

In final yogurt product butter (diacetyl), yogurt (acetaldehyde) and nitrogenous and sharp cheese flavour (sulphur-containing compounds) derive from the metabolic activities of

Leuconostoc, Lactobacillus acidophilus and Lactobacillus lactis

Targets for the improvement of enzyme recovery often include increased secretion efficiency for extracellular enzymes and overcoming of the

organism's own regulatory mechanisms

Distillation is a method of separating chemical substances based on differences in their

volatility

Describe the production of microbially-produced enzymes

Once the organism is selected apart from enzyme productivity, a major consideration is enzyme stability, which can influence the timing, and DSP operations. The level of purification varies considerably depending on whether the enzyme is intra- or extracellular, and on its end use. Strain improvement may be attempted to further enhance enzyme productivity. Targets for improvement often include increased secretion efficiency for extracellular enzymes and overcoming of the organism's own regulatory mechanisms. Today, if a useful enzyme is identified in a microorganism, which is itself difficult to culture, or if little is known of its physiology and biochemistry, other strategies for commercial production can be adopted. Rather than proceeding with extensive research and development programs to facilitate the production of the enzyme by the natural producer organism, the structural gene for the enzyme can be transferred into a selected microorganism. Genetic engineering now makes possible the expression of the gene coding for almost any enzyme, no matter what its origin. Expression in GRAS-listed organisms provides obvious advantages.

A slimy texture of sauerkraut can occur due to overgrowth of

Leuconostoc species

Acetic acid, its salts and vinegar are used in different foods for inhibiting growth and reducing the viability of Gram-positive and Gram-negative bacteria, yeasts, and molds. It is generally bacteriostatic at 0.2% but bacteriocidal above

0.3%

Purification strategy for DNA polymerase from Thermus aquaticus (Taq DNA polymerase) & genetically modified E. coli

1. Production medium + Innoculum development 2. Production fermentation (batch process) 3. Cell harvesting (centrifugation) 3a. (Supernatant) 4. Disruption of collected cells 5. Centrifugation 5a. (Cell debris) 6. Cell-free extract 7. Ammonium sulphate precipitation 8. Centrifugation 8a. (Supernatant) 9. Resuspension of protein precipitate 10. Dialysis 11. DEAE cellulose chromatography 12. Hydroxyapatite chromatography 13. DEAE cellulose chromatography 14. Phosphocellulose chromatography 15. Purified Taq DNA polymerase

Penicillin fermentation require spore concentrations of

5x10^3 spores/ml

The term thermostable for enzymes refers to those enzymes that can catalyze reactions above 60°C. Enzyme tyrosinase from a thermolabile strain of Neurospora sp. denatures in 4 min at 60°C, but from a thermostable strain of the same species denatures in

70min at 60°C

Disulfide bonds

A disulfide bond, also called an S-S bond, or disulfide bridge, is a covalent bond derived from two thiol groups. In biochemistry, the terminology R-S-S-R connectivity is commonly used to describe the overall linkages. The most common way of creating this bond is by the oxidation of sulfhydryl groups. The linkage is also called an SS-bond or sometimes a disulfide bridge and is usually derived by the coupling of two thiol groups.

The inhibition of nucleic acid synthesis

A number of antibiotics interfere with processes of DNA replication and transcription in microorganisms. Drugs with this mode of action have an extremely limited usefulness because they interfere with mammalian DNA and RNA as well

Propeptide

A protein precursor, also called a pro-protein or pro-peptide, is an inactive protein that can be turned into an active form by post-translational modification, such as breaking off a piece of the molecule or adding on another molecule.

Leader peptide

A short peptide (usually 16-30 amino acids long) present at the N-terminus of the majority of newly synthesized proteins that are destined towards the secretory pathway. These proteins include those that reside either inside certain organelles (the endoplasmic reticulum, Golgi or endosomes), secreted from the cell, or inserted into most cellular membranes. Although most type I membrane-bound proteins have signal peptides, the majority of type II and multi-spanning membrane-bound proteins are targeted to the secretory pathway by their first transmembrane domain, which biochemically resembles a signal sequence except that it is not cleaved. They are a kind of target peptide.

List the advantages of using acetic acid in food preservation.

Acetic acid, its salts, and vinegar (which contains 5%-40% acetic acid and many other compounds that give it the characteristic aroma) are used in different foods for inhibiting growth and reducing the viability of Gram-positive and Gram-negative bacteria, yeasts, and molds. Acetic acid is generally bacteriostatic at 0.2% but bactericidal above 0.3% and more effective against Gram-negative bacteria. However, this effect is pH dependent, and the bactericidal effect is more pronounced at low pH (below pH 4.5). It is added to salad dressings and mayonnaise as an anti-microbial agent. It is permitted to be used as a carcass wash.

Coprophilic microorganisms found in the faeces of cattle. They indicate dairy farm originating pollution in the environment and belong to the group of bacteria called

Actinomycetes

Adsorption

Adsorption technique involves adding an enzyme solution to the support (e.g. ion- exchange resins) and washing away the unattached molecules. The association is weak, and the molecules can then be desorbed and removed

What are ergot alkaloids?

Alkaloids are a diverse group of small nitrogen containing organic compounds produced by certain plants and microorganisms. Many are toxic but some have various therapeutic properties. Species of the filamentous fungus Claviceps, which are pathogens of grasses, produce a range of alkaloids. Some of the best known are the ergot alkaloids. These compounds are produced within sclerotia (fruiting bodies) of Claviceps purpurea that develop naturally when this organism infects developing cereal grains. Infected grains become black and are referred to as ergots

The objective in semisynthetic penicillin production is to generate compounds with improved properties such as

All of the above (Acid stability, Resistance to enzymic degradation, Broader spectrum of activity)

What kind of ingredients fermentation media do contain?

All of the above (Carbon and nitrogen sources, Minerals, vitamins and growth factors, Precursors, inducers, elicitors and inhibitors)

Which of the following may be the main factor affecting the final choice of individual raw materials used for fermentation medium?

All of the above (Cost, availability and ease of handling solid or liquid forms, transportation and storage costs, Sterilization requirements, formulation, mixing, complexing and viscosity characteristics that may influence agitation, aeration and foaming during fermentation and DSP, The levels and range of impurities and overall health and safety implications)

In the finishing steps of the DSP which of the following methods are used to prepare the pharmaceutical product for public use?

All of the above (Crystallization, Drying, Freeze-drying)

Development of purification strategy for any pharmaceutical product requires

All of the above (Holistic approach, Communication between each unit processes, Reproducibility of the compound)

Which of the following technique is used during the initial separation of the target product in the DSP?

All of the above (Sedimentation, Filtration, Cell disruption (mechanical and non-mechanical))

Industrial fermenter design, quality construction, mode of operation and the level of sophistication largely depend upon

All of the above (The production organism, The optimal operating conditions required for target product formation, The scale of production)

Some target products are intracellular, including many enzymes and recombinant proteins. Therefore, methods are required to disrupt the microorganismal cell and release these products. Methods use include

All of the above (Use of an equipment called French Press, Autolysis, Osmotic shock)

The presence of which of the following may interfere with the DSP steps and the accompanying product analysis

All of the above (fermentation by-products, media impurities, fermentation additives (such as antifoams))

Centrifugation can be used during the DSP. The major disadvantages of the DSP are

All of the above (high initial capital costs, the noise generated during operation, the cost of electricity)

Factors that have major influences on the filterability, sedimentation and homogenization efficiency of the producer organism during the DSP are

All of the above (morphology, flocculation characteristics, size and cell wall rigidity)

The performance of any fermenter depends on many factors, but the key physical and chemical parameters that must be controlled are:

All of the above (oxygen transfer, pH, temperature and foam production)

Organic acids produced by microorganisms include

All of the above (Lactic acid, Acetic acid, Propionic acid, Ascorbic acid)

In food industry microbial enzymes are used for

All of the above (Starch processing, cheese production, plant juice production)

What are "orphan drug" programs?

An additional problem arises when the potential market cannot afford the product, as in developing countries. In these situations, international agencies such as the UN may be involved in supplying the products. The level of scientific knowledge in a further key factor. Some advances in science result in the rapid development of industrial processes, termed "Scientific push". For example, Fleming's discovery of penicillin in 1928 ultimately led to the establishment of the antibiotic industry in the 1940s. A particularly rapid development was seen with monoclonal antibodies. Their production was first developed in the early 1970s and led to a multi-million dollar industry just a few years. The rapid progress of recombinant DNA technology in recent years has also generated a "push" for many new products and, importantly, this technology can be readily applied to established fermentation processes. Nevertheless, some major markets exist, but at present that science cannot produce the necessary product, e.g. an effective HIV vaccine, drugs for treatment of cancer, CJD, mental disorders, heart disease.

Equipment, which draws air through a graded series of decreasing pore size to trap microbial spores, is called

Andersen Air Sampler

What are antibiotics?

Antibiotics are a group of secondary metabolites defined on the basis of their antimicrobial activity in laboratory tests. Antibiotics are actually rather easy to discover, but few are of medical or commercial value. Many antibiotics are toxic to humans or lack any advantage over antibiotics already in use.

Describe the fermentation of recombinant therapeutic peptides and proteins.

Antibiotics have been the most important group of compounds synthesized by industrial microorganisms. Other major health-care products derived from microbial fermentations and/or bio- transformation are alkaloids, steroids, toxins, vaccines, vitamins and enzymes as well as viable microbial cell preparations used as probiotics. In addition, genetic engineering techniques have made it possible for microorganisms to produce a wide variety of mammalian proteins and peptides that have various therapeutic properties. Apart from these therapeutic agents, which cure or reduce the incidence of disease, many diagnostic products also derive from microorganisms testing for the presence of various health and disease states

What are antifoams and how are they used?

Antifoams are necessary to reduce foam formation during fermentation. Foaming is largely due to media proteins that become attached to the air-broth interface where they denature to form stable foam. If uncontrolled the foam may block air filters, resulting in the loss of aseptic conditions; the fermentor becomes contaminated and microorganisms are released into the environment. There are three possible approaches to controlling foam production - modification of medium composition, use of mechanical foam breakers, and addition of chemical antifoams

List the antimicrobial compounds produced by different starter-culture bacteria.

Antimicrobial compounds produced by different starter-culture bacteria include organic acids (lactic, acetic, propionic); aldehydes, ketones, & alcohols (acetaldehyde, diacetyl, ethanol); hydrogen peroxide; reuterine; & bacteriocins.

Describe the mode of action of antibiotics.

Antimicrobial drugs are either bactericidal (they kill microbes directly) or bacteriostatic (they prevent microbes from growing). The main modes of actions of antibiotics are: The inhibition of cell wall synthesis, The inhibition of protein synthesis, Injury to plasma membrane, The inhibition of nucleic acid synthesis, Inhibiting the synthesis of essential metabolites

Haze in the pear juices is cleared using an enzyme called

Arabinase

Citric acid is generally produced by

Aspergillus niger

Which group of organisms proved to be superior in enzyme production and expression

Bacillus, Aspergillus and Saccharomyces

How are bacteriocins grouped?

Bacteriocin molecules, based on the molecular structures, are subdivided into several groups. Broadly, they are grouped as Class I, which contains lanthionine rings, and Class II, which lacks lanthionine. Bacteriocins without lanthionine are grouped under Class II, currently containing five subgroups.

Briefly explain the potential therapeutic uses of bacteriocins

Bacteriocins are now evaluated for therapeutic use as a substitute for antibiotics and have shown some promising results. Use of bacteriocin-producing probiotics is desirable as a prophylactic for their ability to colonize the GIT and secrete bacteriocin to inactivate pathogens. However, for therapeutic use, purified bacteriocin produced mixed results because some bacteriocins are unstable in in vivo environments. For example, feeding of laboratory animals with purified pedio- cin did not affect the composition of the gut microbiome, which is responsible for maintaining intestinal homeostasis, while nisin did affect microbiome composition. Intragastric administration of purified pediocin was effective in reducing Listeria monocytogenes infection in a mouse model.

Define bacteriocins of lactic acid bacteria

Bacteriocins of lactic acid bacteria are bactericidal to sensitive cells, and death occurs very rapidly at a low concentration. Normally, Gram-positive bacterial strains are sensitive, the spectrum or range of which can vary greatly. Although Gram-negative bacterial cells are normally resistant to bacteriocins of lactic acid bacteria, they become sensitive following impairment of the cell surface lipopolysaccharide structure by physical and chemical stresses. Many bacteriocins are bactericidal against a few related species and strains, but several are effective against many strains from different species and genera.

Briefly discuss how bacteriocin production of a producer strain of lactic acid bacteria can be enhanced.

Bacteriocins' use as food preservative is sometimes limited because of their narrow antimicrobial activity spectra, low solubility and stability, and resistance to intestinal enzymes. Modification of the bacteriocins through bioengineering, such as mutation or substitution of amino acid residues, has been attempted to improve bacteriocin functionality. For example, mutation in amino acids in ring A of nisin improved its antimicrobial spectrum. Likewise, site-directed mutagenesis in nisin-producing strains yielded increased antimicrobial activity against Listeria monocytogenes and Staphylococcus aureus. Solubility of nisin Z was improved by substituting asparagine at position 27 and histidine at position 31 with lysine residues. Sensitivity of microcin J25, produced by Escherichia coli, to chymotrypsin was achieved by substitution of glycine at position 12 with tyrosine without affecting its antimicrobial activity. Introduction of a disulphide bridge in the C-terminal end of sakacin P broadened its antimicrobial spectrum. A chimeric bacteriocin consisting of the C-terminal half of pediocin and the N-terminal half of enterocin A yielded improved antimicrobial activity against Leuconostoc lactis, a dairy product spoilage bacterium. Continued efforts are needed in developing desirable bacteriocins through bioengineering to enhance antimicrobial spectrum and stability during food preservation.

Briefly explain the function of genes in the production of active molecules.

Bacteriocins, in general, are highly susceptible to food environments, including microbial enzymes, pH shift (to neutral or alkaline pH), salts, and other food components. Therefore, it is essential to develop technologies to preserve the activity of bacteriocins in food for at least a certain duration before the expiration of the shelf life of a product. Scientists have employed numerous strate- gies to effectively deliver antimicrobial peptides, including bacteriocins on varieties of foods. For example, bacteriocins have been encapsulated in macrostructures or nanostructures for maintaining activity and controlled release over a period of time. The major advantages of such strategies include loading of large amounts of antimicrobials, homogeneous dispersion into the food system, accessibility to microorganisms, increased interaction and attachment to microbes because of smaller sizes, and protection from food environments and controlled release of active molecules.

What are some disadvantages of using H2O2 in food?

Because of its oxidizing property, it can produce undesirable effects in food quality, such as discoloration in processed meat, and thus has limited use in food preservation. However, its application in some food processing and equipment sanitation is being studied.

The inhibition of protein synthesis

Because protein synthesis is a common feature of all cells, this type of activity does not have selective toxicity. The only selectivity can be due to the differences in ribosomal structures in Prokaryotes and Eukaryotes. Eukaryotic cells have 80S ribosomes, prokaryotic cells have 70S ribosomes. However, mitochondria (important eukaryotic organelles) also contain 70S ribosomes similar to those of bacteria. Antibiotics targeting the 70S ribosomes can therefore have adverse effects on the cells of the host. Among the antibiotics that interfere with protein synthesis are chloramphenicol, erythromycin, streptomycin, & tetracyclines

DSP has the primary aim of efficiently, reproducibly and safely recovering the target product to the required specifications while minimizing the costs. These specifications are

Biological activity and purity

Briefly list differences in gene organizations associated with bacteriocin production in lactic acid bacteria.

Biosynthesis of a bacteriocin, involving transcription, translation, structural modification, and secretion, occur in a concerted way. In pediocin, AcH or PA-1 and similar bacteriocins, probably a single mRNA, is produced for all four genes, which are then translated into four separate proteins (Figure 17.2). As soon as the 62-amino-acid prepedicin is translated in the cytoplasm, the leader peptide directs transport of the molecule outside the cell by the help of Pap or PedD (ABC transporter) and C (helper). During transportation, the catalytic site of protein D recognizes -G-G- at the -1 and -2 positions of prepediocin and cleaves the leader peptide (18 amino acids); the transporter then secretes the 44-amino-acid pediocin into the environment. In an oxidized environment, the four cysteine molecules form two disulfide bonds, one at positions +9 and +14 and another at +24 and +44. The location and mechanism of the immunity protein Pap or PedB in the producing cells are not known. In nisin A production, initially, proteins NisR and NisK induce transcription of the cluster, probably to produce a single mRNA, which is then translated into 11 separate proteins. NisB dehydrates serine and threonine to their respec- tive dehydroamino acids, and NisC with NisB then enables dehydroamino acids to form thio- ether rings with cysteine residues in the molecule. The modified molecule is then translocated through the membrane by NisT, and NisP removes the 14-amino-acid leader peptide, releasing the 34-amino-acid nisin outside the cells. NisE, NisF, and NisG provide extra protection to producer cells against nisin.

Injury to plasma membrane

Certain antibiotics, especially polypeptide antibiotics, bring changes in the permeability of the plasma membrane and these changes result in the loss of important metabolites from the microbial cell. For example, polymyxin B causes disruption of the plasma membrane by attaching to the phospholipids of the membrane.

Give one example of each bacteriocin group.

Class I: Nisin A Class IIa: Pediocin AcH Class IIb: Plantaricin S Class II (non-subgroup): Carnobacteriocin A Class II (no leader peptide): Enterocin L50 Class II (sec-dependent): Enterocin P31 Class III: Helveticin J

Hemicellulase

Class: Hydrolases Source: Bacteria, molds Substrate: Hemicellulose Function/Use: Juice clarification

Lipases

Class: Hydrolases Source: Bacteria, molds Substrate: Lipids Function/Use: Cheese ripening

Proteinases

Class: Hydrolases Source: Bacteria, molds Substrate: Proteins Function/Use: Meat tenderisation, cheese making & ripening

A-Amylase

Class: Hydrolases Source: Bacteria, molds Substrate: Starch Function/Use: Production of dextrins; brewing & baking

Cellulase

Class: Hydrolases Source: Molds Substrate: Cellulose Function/Use: Hydrolyze cellulose; ethanol production, juice extraction

Glucoamylase

Class: Hydrolases Source: Molds Substrate: Dextrins Function/Use: Dextrins to glucose

Pectinases

Class: Hydrolases Source: Molds Substrate: Pectin Function/Use: Clarification of wine, fruit juice, juice extraction

Lactase

Class: Hydrolases Source: Molds, yeasts Substrate: Lactose Function/Use: Glucose or galactose from whey; low lactose milk

Invertase

Class: Hydrolases Source: Yeasts Substrate: Sucrose Function/Use: Production of invert sugar

D-Glucose isomerase

Class: Isomerases Source: Bacteria Substrate: Glucose Function/Use: Glucose to fructose; high fructose corn syrup

D-Glucose oxidase

Class: Oxidoreductases Source: Molds Substrate: D-glucose, oxygen Function/Use: Flavour & colour of liquid egg, juice

Catalse

Class: Oxidoreductases Source: Molds Substrate: H2O2 Function/Use: Removal of H2O2; milk, liquid eggs

Cross-linking

Cross-linking is achieved by making chemical connections between the enzyme molecules to form large aggregates that are insoluble. This is a very stable system

Which of the following techniques are used during the finishing steps of the target product recovery in the DSP?

Crystallization, drying and freeze drying

Production of coagulated milk proteins by lactic acid bacteria results in

Curd formation

Describe the relationship between cystic fibrosis and the release of free bacterial DNA. How genetically engineered DNase preparations can help to reduce symptoms?

Cystic fibrosis is a fatal genetic disorder involving a malfunction in epithelial tissue. The condition is characterized by the presence of thick mucus which is produced in a number of organs, particularly the lungs, where it impairs breathing and increases the risk of microbial infection. As a consequence of infection, part of the immune response involves phagocytes attacking the microorganisms (Pseudomonas aeruginosa, Burkholderia cepacia, Staphylococcus aureus, Haemophilus influenzae). This results in the release of free DNA from both bacteria and phagocytes into the lungs. The DNA is very viscous and further thickens the mucus. Genetically engineered DNAse preparations are now available that can help clear these secretions by breaking up the long DNA strands into small sections to reduce the viscosity of the mucus (e.g. Pulmozyme).

DSP

DSP encompasses all processes following the fermentation. It has the primary aim of efficiently, reproducibly and safely recovering the target product to the required specifications (biological activity, purity, etc.), while minimizing the costs. The target product may be recovered by processing the cells or the spent medium depending upon whether it is an intracellular or extracellular product.

List the types of enzymes used in industry

Detergent enzymes Starch processing enzymes and related carbohydrases Enzymes in cheese production Enzymes in plant juice production Enzymes in textile manufacture Enzymes in leather manufacture Enzymes in the treatment of wood pulps Enzymes as catalysts in organic synthesis

Discuss why diacetyl has limited use as a food biopreservative.

Diacetyl has an intense aroma, and thus its use is probably limited to some dairy-based products in which its flavor is not unexpected. Also, it is quite volatile and thus may lose its effectiveness in foods that are expected to have a long storage life. Under reduced conditions, it is converted to acetoin, which may have reduced antibacterial effects. This will pose difficulties in its use in vacuum-packaged products. The antibacterial action is probably produced by deactivating some important enzymes. The dicarbonyl group (-CO-CO-) of diacetyl reacts with arginine in the enzymes and modifies their catalytic sites.

Describe the mode of antibacterial action of diacetyl

Diacetyl is produced by several species of lactic acid bacteria in large amounts, particularly through the metabolism of citrate. Several studies have shown that it is antibacterial against many Gram-positive and Gram-negative bacteria. Gram-negative bacteria are particularly sensitive at pH 5.0 or below. Diacetyl is effective at approximately 0.1%-0.25%. Recent studies have shown that in combination with heat, diacetyl is more bactericidal than when used alone.

Pyruvate can be used to produce products other than lactic acid. List four such products

End products of pyruvate, other than lactic acid, include acetaldehyde ~ TPP, alpha-acetolactate, propionic acid, CO2.

In transferring an industrial process from the laboratory to the commercial fermenter, several stages can be envisioned. Which of the following is not one of these stages?

End-product marketing

Inhibiting the synthesis of essential metabolites

Enzymatic activity of a microorganism can be competitively inhibited by a substance (antimetabolite) that closely resembles the normal substrate for the enzyme. An example of competitive inhibition is the relationship between the antimetabolite sulfanilamide and para-amino-benzoic acid. In the presence of sulfanilamide, the enzyme that normally converts PABA to folic acid combines with the drug instead of with PABA. This combination prevents folic acid synthesis and stops the growth of the microorganism. Because humans do not produce folic acid from PABA, sulfanilamide exhibits selective toxicity and it affects microorganisms that synthesize their own folic acid but does not harm human hosts.

What is enzyme immobilization?

Enzyme immobilization can be defined as the confinement of enzyme molecules onto/within a support/matrix physically or chemically or both, in such a way that it retains its full activity or most of its activity.

Fermenters with the capacity of 40-80,000L are commonly used to ferment

Enzymes and antibiotics

Describe the different processes used for enzymes immobilization.

Enzymes can be immobilized by several physical, chemical, or mechanical means. Adsorption technique involves adding an enzyme solution to the support (e.g. ion-exchange resins) and washing away the unattached molecules. The association is weak, and the molecules can then be desorbed and removed. In covalent bonding the enzyme molecules are covalently bound to a solid surface (such as porous ceramics) by a chemical agent. The enzyme molecules are accessible to the substrate molecules. In entrapment the enzyme molecules are enclosed in a polymeric gel (e.g. alginate) that has an opening for the substrate molecules to come in contact with the catalytic sites. Cross-linking is achieved by making chemical connections between the enzyme molecules to form large aggregates that are insoluble. This is a very stable system. There are several disadvantages in the enzyme immobilization. Immobilization can reduce the activity of an enzyme. Substrate molecules may not be freely accessible to the immobilized enzymes. The method may not be applicable if the substrate molecules are large. α-Amylase may not be a good candidate for immobilization because its substrate is fairly large starch molecules. Microbial cells can also be immobilized by Aspergillus niger (for citric acid and gluconic acid), Saccharomyces cerevisiae (for alcoholic beverages), & Lactobacillus species (for lactic acid).

What kind of microbial metabolites are used in industry?

Examples of primary metabolites include alcohols such as ethanol, lactic acid, and certain amino acids. Within the field of industrial microbiology, alcohol is one of the most common primary metabolites used for large-scale production.

What kind of fermenters are used during the scale-up process?

Experiments in laboratory flask, which is generally the first indication that a process of commercial interest is possible. The laboratory fermenter, a small scale fermenter, generally of glass 1-10L size, in which the first efforts at scale-up are made. In this fermenter, it is possible to test variations in medium, temperature, pH, and so on, inexpensively because little cost is involved for either equipment or culture medium. The pilot plant stage is usually carried out in equipment 300-3000L in size. Here, the conditions more closely approach the commercial scale; however, cost is not yet a major factor. In the pilot plant fermenter, careful instrumentation and computer control are desirable so the conditions most similar to those in the laboratory fermenter can be obtained. The commercial fermenter itself, generally 10,000-500,000 L

What is Extrinsic Allergic Alveolitis (Hypersensitivity Pneumonitis)?

Extrinsic allergic alveolitis is commonly induced by repeated exposure to large spore concentrations. The dose response relationship has not been fully defined. An environment in which allergic alveolitis occurs more than 10^6 spores/m3 in the atmosphere, but a minimum figure of 10^8 spores/m3 has been suggested for the causation of symptoms.

What kind of microorganisms can cause Extrinsic Allergic Alveolitis (Hypersensitivity Pneumonitis)?

Farmer's lung is the classic form of extrinsic allergic alveolitis. It was first described by Campbell (1932) in a group of Cumbrian Farmers and was associated with the dusty mouldy hay containing actinomycetes. In Britain, the incidence of farmer's lung is greatest in the high rainfall areas of the west and in seasons when the weather during haymaking is wet. Respiratory disease resembling a farmer's lung may also be found in cattle and horses exposed to mouldy hay.

Downstream processing encompasses all processes following

Fermentation

What kind of medium is used to grow industrial microorganisms?

Fermentation

What kind of ingredients are required in fermentation media?

Fermentation media contain carbon sources, nitrogen sources, water, minerals, vitamins and growth factors, precursors, inducers and elicitors, inhibitors, and cell permeability modifiers.

What is fermentation media?

Fermentation media must satisfy all the nutritional requirements of the microorganism and fulfill the technical objectives of the process. The nutrients should be formulated to promote the synthesis of the target product, either cell biomass or a specific metabolite. Use of media in industrial processes may include several inoculum (starter culture) propagation steps. Pilot-scale fermentations are often very different, which may be reflected in differences in their media formulations. Where biomass or primary metabolites are the target product, the objective is to provide a production medium that allows optimal growth of the microorganisms. For secondary metabolite production, such as antibiotics, their biosynthesis is not growth related. Consequently, for this purpose, media are designed to provide an initial period of cell growth, followed by conditions optimized for secondary metabolite production. At this point the supply of one or more nutrients (carbon, phosphorus or nitrogen source) may be limited and rapid growth ceases.

Lipases Use

Foam stabilisation in baking Enhanced cheese ripening

Describe the use of microbial enzymes in food waste management

Food industries generate large volumes of both solid and liquid waste. Waste disposal methods used are physical, chemical, or biological. Biological methods include anaerobic digestion and production of SCPs. Microbial enzymes in converting food waste to value-added products are being extensively studied. Some of the enzymes used in food waste treatment are cellulase, pectinase, hemicellulase, chitinase, & amylase. Amylases can be used to treat starch-containing waste water to produce glucose syrup for use in alcohol production by yeasts. Lactose in whey has been treated with lactase to produce glucose and galactose which are then used in alcohol production by yeast or to produce baker's yeast.

As in the development of any fermentation process, enzyme production processes traditionally begin with the search for a suitable producer organism in which of the below category

GRAS-listed

Pectinases Use

Fruit juice clarification

Cellulase Use

Fruit liqification Solublization of pentason in baking

Mycotoxins contaminating stored grain and other unprocessed material are produced by

Fungi

Which of the following is not a viable approach to control foam production during fermentation?

Genetic modification of the producer microorganism

Cystic fibrosis is a fatal genetic disorder involving a malfunction in epithelial tissue. The condition is characterized by the presence of thick mucus, which is produced in a number of organs, particularly the lungs, where it impairs breathing and increases the risk of microbial infection. This results in the release of free DNA from both bacteria and phagocytes into the lungs. The DNA is very viscous and further thicken the mucus. What kind of preparations are used to clear such mucus?

Genetically engineered DNAse

Which of the following enzyme combinations can be employed to remove molecular oxygen from wine, beer, fruit juices and soft drinks to prevent potentially damaging oxidation that otherwise affects product quality

Glucose coupled with catalase

In the wine making releasing the terpenes that are important constituents of the wine bouquet is achieved via the use of which of the following enzymes?

Glycosidases

Lactic acid below pH 5.0 has bacteriocidal effect against

Gram-negative bacteria

Microorganisms which produce lactic acid as well as ethanol are termed as:

Heterolactic

Glucose isomerase

High fructose corn syrup

What needs to be done before pasteurizing milk small amounts of H2O2?

Hydrogen peroxide is permitted in refrigerated raw milk and raw liquid eggs (ca. 25 ppm) to control spoilage and pathogenic bacteria. Before pasteurization of these foods, catalase (0.1-0.5 g/ 1000 lb [455 kg]) is added to remove the residual H2O2. Its antibacterial action is attributed to its strong oxidizing property and its ability to damage cellular components, especially the membrane.

Invertase Use

Hydrolysis of sucrose in confectionary Flavour development in fruit juices

Covalent bonding

In covalent bonding the enzyme molecules are covalently bound to a solid surface (such as porous ceramics) by a chemical agent. The enzyme molecules are accessible to the substrate molecules

In drafting the proposal to produce any new fermentation product, and throughout its development, a great deal of input must come from disciplines other than microbiology. What are these disciplines?

In drafting the proposal to produce any new fermentation product, and throughout its development, a great deal of input must come from disciplines other than microbiology. Major contributions are required from among others, biochemists, geneticist, molecular biologists, chemists, chemical and process engineers, mathematicians and computer technologists

Entrapment

In entrapment the enzyme molecules are enclosed in a polymeric gel (e.g. alginate) that has an opening for the substrate molecules to come in contact with the catalytic sites

List five potential applications of bacteriocins of lactic acid bacteria as food preservatives.

In foods that can contain injured Gram-negative bacteria, bacteriocins can also be effectively used to kill them. They are more effective when used in minimally heat-processed foods in suitable combinations of two or more (e.g., nisin and pediocin together). Bacteriocin preparation effectively reduced the Gram-positive spoilage (Leu. mesenteroides) and pathogenic (Lis. monocytogenes) bacteria as well as Gram-negative pathogens (Salmonella and Esc. coli O15:H7) during six weeks of storage at 4°C. Bacteriocins are examined in combination with other antimicrobials, such as acids, salts, spice extracts, high pressure, or other bacteriocins, for synergistic effects to control both Gram-positive and Gram-negative foodborne pathogens in food. There are many other food products in which bacteriocins of lactic acid bacteria can be used effectively as preservatives.

Thiol group

In organic chemistry, a thiol is a compound that contains the -SH functional group, which is the sulfur analog of a hydroxyl or alcohol group. The functional group is referred to as either a thiol group or a sulfhydryl group. Thiols are more traditionally referred to as mercaptans. Thiols and alcohols have similar molecular structure, although the C-S-H bond angle is closer to 90° than the C-O-H bond angle of alcohol. In the solid or liquid state, the hydrogen bonding between individual thiol groups is weak, the main cohesive force being van der Waals interactions between the polar sulfur centers.

Discuss the advantages of using small amounts of H2O2 in raw milk to inhibit psychrotrophic bacteria, such as Pseudomonas species.

In refrigerated raw milk, the antibacterial action produced by adding nongrowing cells of mesophilic lactic acid bacteria is thought to be a result of the ability of H2O2 of bacteria to activate the lactoperoxidase-thiocyanate system in raw milk. Raw milk contains lactoperoxidase enzymes and thiocyanate (SCN-). In the presence of H2O2, lactoperoxidase generates a hypo-thiocyanate anion (OSCN-), which, at milk pH, can be in equilibrium with hypothiocyanous acid (HOSCN). Both OSCN- and HOSCN are strong oxidizing agents and can oxidize the -SH group of proteins, such as membrane proteins of Gram-negative bacteria that are especially susceptible. In addition, this system has inhibitory activity against other bacteria, fungi, and viruses. It is inactivated by pasteurization.

Which of the following technique is not used during the recovery of the target product in the DSP?

Incubation

What is industrial microbiology?

Industrial microbiology is the discipline that uses microorganisms, usually grown on a large scale to produce valuable commercial products. Microbial products of industrial interest are of several major types and the most commonly produced microbial product is antibiotic. Microorganisms have proved to be particularly useful for industrial applications due to their ease of mass cultivation, speed of growth, and use of cheap substrates like wastes, o and the diversity of potential products

Malliard reaction

It occurs between reducing sugars and principally free amino acids and peptides (usually from proteins) when heated. Actually, the term 'Maillard reaction' is a misnomer. It is not a single reaction but a whole complex of reactions whose pathway and outcomes depend critically on factors such as pH and temperature. However, for our purposes here, it is the mechanism that allows products to brown at much lower temperatures than needed for caramelisation of sugars. The reaction is also known as the browning reaction, non-enzymatic browning and melanoidin formation.

What is the name of the enzyme employed in confectionary manufacture? e.g. soft- centered chocolates?

Invertase

Give examples of the use of microbial enzymes in food industry

Invertase (β-fructofuranosidase) was the first enzyme from Saccharomyces cerevisiae to be immobilized for use on an industrial scale. The conversion of sucrose to glucose and fructose using this immobilized invertase replaced conventional acid hydrolysis methods. Invertase is now also obtained from other yeasts or filamentous fungi, e.g. A. niger and A. oryzae. Apart from syrup production, it is employed in confectionery manufacture, e.g. soft-centered chocolates. Lactase (β-galactosidase) is employed in several industrial processes that require the hydrolysis of lactose from milk. Commercial lactase is obtained from Kluyveromyces marxianus, A. niger or A. oryzae. This is required for infants who are lactose intolerant, and in regions of the world where a large population exhibit lactose-intolerance, e.g. Africa and South-East Asia Lactose hydrolysis is also useful in the manufacture of products such as ice cream, as the low solubility of this disaccharide leads to crystal formation that may give an unpleasant sandy texture. Also, its conversion to glucose and galactose increases the sweetness. Rennet preparations from the stomach of calves and lambs have been used in cheese production for thousands of years. These rennets contain the enzyme rennin (chymosin, an aspartic protease). The enzyme rennin performs limited proteolysis of milk protein (casein) to form curds at the start of cheese making. Animal rennets, particularly from calves, predominated in cheese manufacture until the 1960s when a shortage of animal rennet occurred. Specific fungal proteases, with similar properties to calf chymosin, were then developed as microbial rennet e.g. proteases from Rhizomucor miehei and R. pusillus that overcame the shortage and facilitated the production of so-called "vegetarian" cheese. More recently, the calf chymosin gene has been introduced into several microorganisms, including E. coli, K. lactis, Aspergillus nidulans and A. niger var. awamori. These genetically engineered microorganisms can express and secrete the enzyme. Microbial lipases are also used in dairy products, especially cheeses, for the hydrolysis of fatty acid esters to accelerate flavor development

List the advantages of using lactic acid in food preservation.

Lactic acid and its salts are used in food more for flavor enhancement than for their antibacte- rial effect, especially when used above pH 5.0. However, recent studies have shown that they have a definite antibacterial effect when used in foods at 1%-2% levels even at or above pH 5.0. Growth of both Gram-positive and Gram-negative bacteria is reduced, indicating increased bacteriostatic action. Below pH 5.0, lactic acid can have a bactericidal effect, especially against Gram-negative bacteria. It may not have any fungistatic effect in the food environment. It is used in many processed meat products and has also been recommended as a carcass wash.

Thioether rings

Lanthionine rings are formed after translation of pre-bacteriocin in the cytoplasm and before transportation through the ABC transporter by enzymatic dehydration of l-serine to dehydroalanine and l-threonine to dehydrobutyrine and formation of thioether rings.

Extrinsic allergic alveolitis is commonly induced by repeated exposure to

Large microbial spore concentrations

Describe the actinomycetes as sources of pollutants in aerobic environments.

Many actinomycetes resemble fungi rather than bacteria in so far as they produce an aerial mycelium bearing a large number of spores. When the substrate is disturbed, these spores easily become detached and launched into the air. In the household environment, studies have indicated that thermophilic actinomycetes might contaminate the atmosphere of homes from humidifiers in hot-air central heating systems. In the farm environment, ripening and stored crops and mushroom composts provide vast sources of spores. These can easily become airborne when crops are harvested or subsequently moved either as feed to livestock or for sale, or when the composts are disturbed.

What is antibiotic resistance?

Many bacterial diseases, previously treatable with antibiotics, have become resistant to antibiotics. Superbugs are bacteria that are resistant to several antibiotics. Drug resistance factors are transferred horizontally between bacteria. Resistance may be due to enzymatic destruction of a drug, prevention of penetration of the drug to its target site, cellular or metabolic changes at target sites, alteration of the target site, or rapid efflux of the antibiotic. The discriminating use of drugs in appropriate concentrations and dosages can minimize resistance.

Briefly discuss how food proteins and food lipids are transported and metabolized by starter-culture bacteria.

Many starter-culture bacteria metabolize lipids poorly. However, molds have better lipid metabolism systems. Triglycerides and phospholipids are hydrolyzed outside of the cells by lipases, produced by the microorganisms, releasing fatty acids and glycerol and glycerides (monoglycerides or diglycerides). Fatty acids can diffuse through the membrane into the cells and be metabolized. Some fatty acids are incorporated in the membrane. Hydrolysis of glycerides, especially those with small fatty acids, such as butyric acid, can cause hydrolytic rancidity of the products. Oxidation of unsaturated fatty acids by microorganisms, especially molds, can produce many flavor compounds, either desirable or undesirable.

Proteases

Meat tenderization Flavour & colour in juices Bread quality in baking Enhanced cheese ripening Brewing

Bioactive metabolite should be "well characterized" before a pharmaceutical discovery becomes commercial. Which of the following is not part of this characterization process?

Medium type used for its fermentation

Describe the use of microbial enzymes in food industry

Microorganisms have been used in food fermentation since ancient times and fermentation processes are still applied in the preparation of many of the food items. Microbial enzymes play a major role in food industries because they are more stable than plant and animal enzymes. They can be produced through fermentation techniques in a cost-effective manner with less time and space requirement, and because of their high consistency, process modification and optimization can be done very easily. Many of these enzymes find numerous applications in various industrial sectors, e.g. amylolytic enzymes find applications in food, detergent, paper and textile industries. They are used for the production of glucose syrups, crystalline glucose, high fructose corn syrups, maltose syrups, etc. Enzymes like proteases, lipases or xylanases have wide applications in food sectors.

Fermentation factors affecting DSP include the properties of microorganisms, particularly their

Morphology, flocculation characteristics and cell wall rigidity

Describe mycotoxins

Mycotoxins are naturally occurring toxins produced by certain moulds (fungi) and can be found in food. The moulds grow on a variety of different crops and foodstuffs including cereals, nuts, spices, dried fruits, apples and coffee beans, often under warm and humid conditions. Mycotoxins can cause a variety of adverse health effects and pose a serious health threat to both humans and livestock. The adverse health effects of mycotoxins range from acute poisoning to long-term effects such as immune deficiency and cancer.

Describe nanoencapsulation technology.

Nanoencapsulation is becoming an attractive strategy for delivery of antimicrobial peptides, including bacteriocins for food preservation and in pharmaceutical applications. Nanostructures usually fall within the 1 nm-100 nm range; however, size may increase (<500 nm) after the functional molecule incorporation. The physicochemical properties, such as optical property, catalytic property, interaction with host tissues and food, of nanostructures differ greatly from the bulk materials. For encapsulation and delivery of antimicrobials for food application, several nanoencapsulation strategies have been developed: nanoliposome, nanoemulsion, lipid nanovesicles, nanofibers, carbohydrate dendrimers, and self-assembled peptides. In addition, nanostructures using silver, zinc, and gold have been used to carry antimicrobial peptides for other applications. Nanoemulsions have been used for delivery of nisin, lysozyme, etc. on their surface. It consists of two immiscible liquids, such as oil and water, which are prepared in the form of droplets. Similarly, solid lipid nanoparticles (SLN ~ 140 nm) are produced using a lipid, and it was able to maintain nisin activity for 20 days. Carbohydrate nanoparticles (60-90 nm) were prepared using phytoglycogen from corn, which was chemically modified to create a dendrimer structure to carry nisin. The nisin-loaded dendrimer maintained nisin activity over 40 days and effectively inactivated Listeria monocytogenes in a model food system. Nanofibers are made of poly (d,l-lactide) and polyethylene oxide dissolved in N,N-dimethylformamide and are used for delivery of several bacteriocins.

The enzyme used in the de-bittering of grapefruit and bitter oranges is called

Naringinase

The polyene antifungal agent produced by Streptomyces species and used as surface antimycotic agent for food (e.g. cheeses) is called

Natamycin

List the names of the occupational allergenic diseases.

Occupational allergenic diseases include bagassosis, mushroom worker's lung disease, Humidifier Fever, & byssinosis (cotton and other fibres).

Development of drugs targeted at rare diseases may not be economically viable for commercial companies. In some overseas countries, their development can be achieved through government-sponsored programs called

Orphan drug programs

Describe the commercial production of penicillin

Penicillin is produced by a fed-batch process carried out aseptically in stirred tank fermenters of 40,000-200,000L capacity. The fermentation involves an initial vegetative growth phase followed by the antibiotic production phase. Throughout the process, the oxygen level is very important and must be maintained at 25-60 mmol/L/h. However, this is not straightforward, because the oxygen transfer rate is affected by the viscosity, which increases as the fermentation progresses. Various carbon sources have been adapted for penicillin production, including glucose, lactose, sucrose, ethanol and vegetable oils. About 65% of the carbon source is metabolized for cellular maintenance, 25% for growth and 10% for penicillin production. The mode of "feeding" of a particular carbon source is vitally important, as it can influence the production of secondary metabolites. Inoculum development is usually initiated by adding lyophilized spores to a small fermenter at concentration of 5x103 spores/ml. Fungal mycelium may then be grown up until there is sufficient to inoculate the production of fermenter. Initially there is vegetative growth phase devoted to the development of biomass, which doubles every 6 hours. This high growth rate is maintained for the first 2 days. To ensure an optimum yield of penicillin in the following production phase, the mycelium must develop as loose pellets, rather than compact forms. During the following production phase, the carbon source is fed at a low rate and penicillin production increases. This continues for a further 6-8 days, provided that appropriate substrate feeds are maintained. Penicillin is excreted into the medium and is recovered at the end of fermentation. Whole broth extraction may be performed, but can lead to downstream processing problems, as additional materials leach from the mycelium. Usually, penicillin recovery follows removal of mycelium using rotary vacuum filters, the efficiency of which may be affected by the culture media composition, particularly its proteinaceous components. Recovered mycelium is then washed to remove residual penicillin, prior to its use as animal feed or fertilizer

Bromate replacement

Potassium bromate is a powerful oxidizing agent that chemically ages flour much faster than open air. Potassium bromate bleaches dough and enhances its elasticity by strengthening its network of molecular bridges, which makes for the formation of tiny, thin-walled bubbles as the bread rises. The end -product is fluffy, soft and unnaturally white. Ideally, that end product is also entirely devoid of potassium bromate, which changes to potassium bromide, a harmless by-product, during baking. In 1982, researchers in Japan published the first of a series of studies showing that potassium bromate causes cancer in the thyroids, kidneys and other body parts of rats and mice. As a result of these findings, countries around the world banned the additive, but the U.S. Food and Drug Administration held back, in part because the amount of potassium bromate that remains in bread after baking should be negligible: less than 20 parts per billion (ppb).

Glucose oxidase

Prevention of Malliard browning reactions Bromate replacer in baking Oxygen scavenger in fruit juices

Amylases & amyloglucosidase

Production of fermentable sugars in baking & brewing Starch liquification Fruit juice clarification

List the advantages of using propionic acid in food preservation.

Propionic acid and its salts are used in food as a fungistatic agent, but they are also effective in controlling growth and reducing viability of both Gram-positive and Gram-negative bacteria. Gram-negative bacteria seem to be more sensitive at pH 5.0 and below, even at acid levels of 0.1%-0.2%. Propionic acid is used to control molds in cheeses, butter, and bakery products and to prevent growth of bacteria and yeasts in syrup, applesauce, and some fresh fruits.

Pseudomonas species responsible for the spoilage of refrigerated products belong to the group of

Psychrotrophic bacteria

Describe the recovery of microbially-produced enzymes

Recovery of the enzyme generally depends upon precipitation from an aqueous solution, although some enzymes may be marketed as stabilized solutions. In the bran process, the enzyme is extracted from the koji (the name given to the mass of material permeated with the mold mycelium) into an aqueous solution by percolation. In the liquid processes, the microbial cells are filtered from the beer. The enzyme may be precipitated by addition of solvents, such as acetone or aliphatic alcohols, to the aqueous enzyme solution, either directly or after concentration by vacuum evaporation at low temperature. The precipitated enzyme may be filtered and dried at low temperature, for example in a vacuum shelf dryer. The dry enzyme powders may be sold as undiluted concentrates on a potency basis or, for most applications, may be diluted to an established standard potency with an acceptable diluent. Some common diluents are salt, sugar, starch, and wheat flour. Most commercial enzymes are quite stable in the dry form, but some require the presence of stabilizers and activators for maximum stability and efficiency in use.

What is scale-up?

Scale-up of an industrial process is the task of the biochemical engineer, one who is familiar with gas transfer, fluid dynamics, mixing and thermodynamics. In transferring an industrial process from the laboratory to the commercial fermenter, several stages can be envisioned.

Some scientific advances, such as the Fleming's discovery of penicillin, may result in the rapid development of industrial processes which are called

Scientific push

Which one of the below is not one of the techniques used during the product purification step of the DSP

Sedimentation

Briefly explain the use of antimicrobial properties of yeasts to preserve foods.

Several yeast isolates normally present on the surface of fruits and vegetables are reported to prevent spoilage of the produce by molds. Some of the inhibitory compounds are small proteins, whereas others are enzymes. Cells of one such yeast isolate were found to adhere tightly with the mold mycelium and produce β-gluconase, which degrades the cell wall of the molds and kills them. Because many of these yeasts are normally present in fruits and vegetables that are eaten raw, they are not considered pathogenic, and thus can be used in place of fungicides to enhance the preser- vation of fruits and vegetables.

Describe two different types of fermentation systems.

Solid State: Non-stirred, non-aerated and are not operated aseptically Liquid State: Stirred, aerated and aseptic

Under what conditions can some lactic acid bacteria generate sufficient quantities of H2O2 to inhibit other microorganisms in a food system?

Some lactic acid bacteria produce H2O2 under aerobic conditions of growth, and, because of the lack of intracellular catalase, pseudocatalase, or peroxidase, they release it into the environment to protect themselves from its antimicrobial action. Some strains can produce, under proper growth conditions, enough H2O2 to induce bacteriostatic (6-8 μg/mL) but rarely bactericidal action (30-40 μg/mL). It is a strong oxidizing agent and can be antimicrobial against bacteria, fungi, and viruses (also bacteriophages). Under anaerobic conditions, very little H2O2 is expected to be produced by these strains.

What is an Andersen Sampler? Describe its use with examples.

Spore counts can be done using an Andersen Air Sampler, which draws air through a graded series of decreasing pore size. An agar plate is placed under each grid to collect microorganisms. Air velocity increases with decreasing grid openings, therefore, increasingly smaller particles land on successive agar plates.

What are stored unprocessed plant food materials?

Stored unprocessed plant food materials are essentially divided into 3 categories - durable products (e.g. grain), semi-perishable products (e.g. apples and root vegetables), & perishable products (e.g. soft fruits and vegetables).

Gram-positive bacteria which can cause earthy taints and odours to drinking water belong to the genus

Streptomyces

What strategies are used to improve functionality of bacteriocins?

Synthetic polymers are widely used as packaging materials, and more recently, biopolymers have been used because of their high water vapor permeability, environmental concerns, and their potential for incorporating active components. Biopolymers are made of natural materials, including carbohydrates, proteins, lipids, and composites. Advances in nanotechnology also helped develop packaging materials with improved functionality, such as active packaging. Active packaging became an industry trend because of its ability to modify the internal environment, resulting from direct interaction of packaging materials with the food. This enabled production of high- quality products with fresh-like appearance and extended shelf life. Incorporation of antimicrobial compounds, such as nisin, into the packaging material (bioactive packaging) to control microbes on the surface of food products can improve safety and prolong shelf life. Another important attribute of active packaging is that it can be fabricated to allow controlled or slow release of the active compounds for long duration. This will slow down the bacterial growth kinetics, rendering it safe for human consumption.

The inhibition of cell wall synthesis

The cell wall of a bacterium consists of a macromolecular network called peptidoglycan. Peptidoglycan is found only in bacterial cell walls. Penicillin prevents the synthesis of intact peptidoglycan. Consequently, the cell wall is greatly weakened, and the cell undergoes lysis. Because penicillin targets the cell wall synthesis, only actively growing cells are affected by these antibiotics. Also, because human cells do not have peptidoglycan cell walls, penicillin has very little toxicity for host cells

List the factors involved in product development.

The development of any new fermentation product on many factors, including the market, the current level of scientific knowledge and, the regulatory environment

At pH 6.0, why are propionic and acetic acids more antibacterial than lactic acid?

The dissociation constants (pKa) are 4.8 for acetic, 4.9 for propionic, and 3.8 for lactic acid. Thus, at most food pH (5.0 and above), the undissociated fractions of the three acids can be quite low, the lowest being for lactic acid. The lower antimicrobial effectiveness of lactic acid is probably a result of its low pKa. The antimicrobial action of the undissociated molecules is pro- duced by dissociation of the molecules in the cytoplasm following their entry through the mem- brane. H+ released following dissociation initially reduces the transmembrane proton gradient and neutralizes the proton motive force and then reduces the internal pH, causing denaturation of proteins and viability loss. However, other studies have suggested that these weak acids produce antimicrobial action through the combined effects of undissociated molecules and dissociated ions. The acids can also induce sublethal injury of the cells and increase their chance of viability loss. Undissociated molecules as well as dissociated ions can induce cellular injury.

List three features of plasmid-encoded bacteriocins of lactic acid bacteria.

The limited available information has revealed that the structural genes encoding pre-bacteriocin molecules of lactic acid bacteria can be encoded in a plasmid (e.g., pediocin AcH or PA-1), in the genome (e.g., sakacin P), or in a genome-integrated transposon (e.g., nisin A) of a producer strain. With plasmid-encoded bacteriocins, several variations are observed: A single plasmid can encode only one bacteriocin (e.g., pediocin AcH or PA-1) or more than one bacteriocin (e.g., lactococcin A, B, and M); the same bacteriocin can be encoded in different-size plasmids in the same species (e.g., lactococcin A in three separate strains of Lac. lactis) or different species (e.g., pediocin AcH in Ped. acidilactici, Ped. pentosaceus, Ped. parvulus, and Lab. plantarum); or a strain producing more than one bacteriocin that can be encoded in different plasmids (e.g., carnobacteriocin A and carnobacteriocin B1 and B2 are encoded in two plasmids in a Car. piscicola strain).

What is involved in fermenter design and construction?

The main function of a fermenter is to provide a suitable environment in which an organism can efficiently produce a target product that may be cell biomass, a metabolite or bioconversion product. The performance of any fermenter depends on many factors, but the key physical and chemical parameters that must be controlled are agitation rate, oxygen transfer, pH, and temperature and foam production. For industrial processes, fermenters with capacities up to several hundred thousand liters are used. Their design, quality construction, mode of operation and the level of sophistication largely depend upon the production organism, the optimal operating conditions required for target product formation, the product value and the scale of production.

Development of any new fermentation product depends on many factors. These factors usually are

The market, current level of scientific knowledge and the regulatory environment

How does the small-scale fermentation media design differ from industrial scale ones?

The media adopted also depend on the scale of the fermentation. For small-scale laboratory fermentations pure chemicals are often used in well-defined media. However, this is not possible for most industrial-scale components that may account for up to 60-80% of process expenditure. Industrial-scale fermentations primarily use cost-effective complex substrates, where many carbon and nitrogen sources are almost indefinable. Most are derived from natural plant and animal materials, often byproducts of other industries, with varied and variable composition. The effects of such batch-to-batch variations must be determined. Small-scale trials are usually performed with each new batch of substrate, particularly to examine the impact on product yield and product recovery.

During Penicillin production which of the following is most important aspect?

The mode of feeding of a carbon source

Prepeptide

The most common definition is that the pre-peptide holds the signal that tells the cell where the protein should be. For example, a pre-peptide can be the signal that tells the cell that this protein must go to the outer membrane.

What kind of organisms are the "superbugs"?

The most threatening "super-bugs" are methicillin-resistant S. aureus (MRSA), vancomycin-intermediate resistant S. aureus (VISA), and vancomycin resistant enterococcus (VRE). Drug resistant strains of S. pneumoniae (DRSP) are also emerging as community acquired infections. Penicillin, macrolide, and fluoroquinolone resistance is rapidly increasing among strains of S. pneumoniae. "Increasing resistance to antibiotics has bred new strains of killer bacteria. Experts say if we don't find new drugs soon, a cut on finger could be fatal"

Describe the nature of microbial damage on stored unprocessed plant food materials.

The nature of the microbial damage includes a decrease in viability, which is important for the seed stock; discoloration, particularly of the embryo, due to invasion by fungal mycelium; biochemical changes, e.g. the production of fatty acids, giving rancid odor and flavor; loss of mass; & production of mycotoxins.

Why is semisynthetic penicillin produced?

The objective in semisynthetic penicillin production is to generate compounds with improved properties - acid stability, resistance to enzymatic degradation, & broader spectrum of activity. The basic structure of penicillin is 6-aminopenicillanic acid (6-APA). The 6-APA can serve as a precursor of cephalosporins, it is often used as the starting material for their semisynthetic production

List the steps involved in product recovery and purification during DSP

The steps in product recovery are sedimentation, centrifugation, broth conditioning, filtration, & cell disruption. In product purification, the steps are chromatography, dialysis & electrodialysis, & distillation.

List two important similarities in the amino acid sequence of cystibiotics that are related to their bactericidal property.

The subgroup of cystibiotics has, at present, 14 bacteriocins and has two or four cysteines that form one or two disulfide rings in an oxidized environment (outside cytoplasm). Cystibiotics with two disulfide rings have greater bactericidal effectiveness than those with one disulfide ring.

What are microbial primary and secondary metabolites? How are they produced?

There are two basic types of microbial metabolites: primary and secondary. A primary metabolite is the one that is produced during the primary growth phase of the microorganism. Whereas a secondary metabolite is the one that is formed near the end of the growth phase, frequently at, near, or during the stationary phase of growth. Each secondary metabolite is formed by only a relatively few organisms. Secondary metabolites are not essential for growth and reproduction.

If a pharmaceutical substance is subject to destruction/decomposition or change in response to heat it is called

Thermolabile

Describe why a "Holistic approach" should be selected during the development of industrial purification strategy.

These factors have major influences on the filterability, sedimentation and homogenization efficiency. The presence of fermentation byproducts, media impurities and fermentation additives, such as antifoams, may interfere with DSP steps and accompanying product analysis. Consequently, a holistic approach is required when developing a new industrial purification strategy. The whole process, both upstream and downstream factors, needs to be considered. For example, the choice of fermentation substrate influences subsequent DSP.

Oxygen scavengers

They effectively prevent oxidative damage in a wide range of food constituents such as (i) oils and fats to prevent rancidity, (ii) both plant and muscle pigments and flavours to prevent discolouration (e.g. meat) and loss of taste and (iii) nutritive elements, e.g., vitamins to prevent loss of the nutritional value

USP

USP involves all factors and processes leading to, and including, the fermentation, and consists of 3 main areas. The first relates to aspects associated with the producer organism. The second aspect involves fermentation media. The third component relates to the fermentation

Cottage cheese is an

Unripened cheese

Certain yeasts, including strains of S. cerevisiae, produce several proteins that have limited antimicrobial properties. These proteins are designated as killer toxins and are called

Zymocins

Rennet preparations contain the enzyme rennin which is a chymosin

an aspartic protease

USP involves all factors and processes leading to, and including, the fermentation, and consists of 3 main areas:

aspects associated with (a) the producer organism, (b) fermentation media, (c) fermentation

List the different groups of fermented dairy products

- milk, - butter, - yogurt, & - cheese.

Describe the coffee fermentations

- natural (dry) - washed - semi-washed

The mechanisms of antibacterial action of nitrite in fermented meat products are not properly understood, but the inhibitory effect might be due to the

All of the above (reactions with some enzymes in vegetative cells and germinating spores, restriction of the bacterial use of iron, and interference with membrane permeability, thereby limiting transport)

Carbon dioxide generated by baker's yeast during bread making can be controlled by

All of the above (the quantity of yeast added, level of fermentable sugars present, the temperature)

Describe the microbially-mediated production of ascorbic acid

Annual production of ascorbic acid is now over 40.000 tonnes. The established process involves chemical stages and a microbial biotransformation. It starts with the chemical catalytic reduction of D-glucose to D-sorbitol, a polyhydric alcohol. D-Sorbitol is then oxidized to L-sorbose using Acetobacter suboxydans or Acetobacter xylinum. Media for this biotransformation step consist of glucose, yeast extract or corn steep liquor, calcium carbonate and D-sorbitol. The biotransformation is performed at 30°C under vigorous aeration and within 1-2 days a 90-95% conversion is achieved. L-Sorbose is recovered from the medium following filtration and concentration of the filtrate to syrup. This sugar crystallizes on cooling and about 65% is recovered, based on starting material. The L-sorbose is then chemically converted to ascorbic acid. A much more direct route from glucose to ascorbic acid has now been made possible by the introduction of a gene encoding reductase from Corynebacterium into Erwinia. This simplifies the process to a single bio-transformation and a single chemical step.

Homolactic

Any form of fermentation that produces a single acid, but especially the anaerobic conversion of pyruvic acid into lactic acid with concomitant oxidation of NADH to NAD.

Aspergillus oryzae

Aspergillus oryzae is used in fermentation of several oriental foods, such as sake, soy sauce, and miso. It is also used as a source of some food enzymes. Asp. niger is used to produce citric acid and gluconic acid from sucrose. It is also used as a source of the enzymes pectinase and amylase.

Homolactic bacteria

Bacteria of several gram-positive genera, including Lactobacillus, Leuconostoc, and Streptococcus, are collectively known as the lactic acid bacteria (LAB), and various strains are important in food production. During yogurt and cheese production, the highly acidic environment generated by lactic acid fermentation denatures proteins contained in milk, causing it to solidify. When lactic acid is the only fermentation product, the process is said to be homolactic fermentation; such is the case for Lactobacillusdelbrueckii and S. thermophilus used in yogurt production.

Why is the bifidus pathway of the metabolism of hexose also called the fructose-phosphate shunt? What are the end products?

Bifidobacterium species metabolize hexoses to produce lactate and acetate by the fructose-phosphate shunt or bifidus pathway. For every two molecules of hexoses, two molecules of lactate and three molecules of acetate are produced without generation of any CO2. From two molecules of fructose-6-phosphate, generated from two molecules of glucose, one molecule is converted to produce one 4C erythrose-4-phosphate and one acetyl-phosphate (which is then converted to acetate). Another molecule of fructose-6-phosphate combines with erythrose-4-phosphate to generate two molecules of the 5C xylulose-5-phosphate through several intermediate steps. Xylulose- 5-phosphates are then metabolized to produce lactates and acetates by the method described in the non-oxidizing part of heterolactic fermentation. The end products produced are d(-)-lactate, ethanol, and CO2.

Fermented meat products are produced by first mixing meat, fat, salt, sugar, curing agent, spices and selected starter-culture bacteria and the fermentation process is a

Both natural and controlled one

Describe the microbially-mediated production of carotenoids

Carotenoids are yellow to orange-red pigments that are ubiquitous in nature functioning as precursors of vitamin A. They are also effective antioxidants. In humans these properties have been linked to a presumed protection against cancer. Several carotenoids are widely used as natural food colorants for butter, ice-cream and other products. They may also be added to poultry feed to enhance the color of skin and egg yolk, and to fish feed for coloring the flesh

Agglutinins can induce

Clumping of starter culture cells

Describe the microbially-mediated production of vitamin B

Cobalamin (vitamin B12) is used as a food supplement and is particularly important in the treatment of pernicious anaemia. The 2-phase industrial production process employs the bacteria Propionibacterium shermanii or Pseudomonas denitrificans. As with many other fermentation processes, feed-back repression must be avoided. Consequently, the first stage of the fermentation is conducted under anaerobic conditions in the absence of the B12 precursor. This leads to the accumulation of the intermediate, cobinamide which is converted to vitamin B12 in the second phase when the culture is aerated. On purification it is isolated in the form of cyanocobalamin. Riboflavin (vitamin B2) is used to fortify processed foods, particularly breakfast cereals and soft drinks. It can be produced chemically or by fermentation processes often using the yeasts (e.g. Candida flareri). Annual production via fermentation is around 600 tonnes. Each fermentation is divided into 2 stages: the first promotes growth and the second maximizes riboflavin production. This is achieved through the restriction of growth by controlling the periodic or continuous addition of the carbon source or a micronutrient such as iron. The riboflavin is secreted into the medium, but some remains cell-bound and is released by heat treatment prior to further purification. Riboflavin can also be obtained from a genetically modified strain of Bacillus subtilis or Lactobacillus lactis that is faster growing than the yeasts and produces a higher amount of riboflavin. It is identical to that produced by chemical means and its use to increase the nutritional value of fermented food and feed is approved in some countries.

Washed

Coffee cherries are pulped then soaked in water for 24hrs. The fermentation process loosens the pulp, then rinsed off and dried. Washed coffees produce clean, consistent flavours (Central America and Africa).

Natural (dry)

Coffee fruits are dried intact on the coffee seed slowly over 2-3 weeks. The drying process creates a natural fermentation yielding full body, low acidity and deep flavours. The dried cherry skin is later hulled off. Processed in more rural areas with limited availability of clean water (Brazil, Ethiopia, Yemen).

In unsalted butter which of the following bacteria can grow in the water phase and produce flavor defects

Coliforms, Enterococcus, and Pseudomonas

Describe the butter production via microbial processes

Cultured butter is usually prepared from pasteurized cream ripened with bacteria for 24-48 hours prior to churning. Lactococcus lactis ssp. diacetylactis and Leucomostoc citrovorum are often used, which produce acid and flavor compounds, particularly diacetyl. The microbiological quality of butter depends on the quality of cream and the sanitary conditions used in the processing Growth of bacteria (Pseudomonas spp.), yeasts (Candida spp.) and molds (Geotrichum candidum) on the surface causes flavor defects (putrid, rancid, or fishy) and surface discoloration. In unsalted butter, coliforms, Enterococcus, and Pseudomonas can grow favorably in the water phase (which has nutrients from milk) and produce flavor defects Cultured buttermilk is a dairy product generally produced by inoculating partially skim milk through controlled fermentation with specific starter-culture bacteria. It has ca 0.8% lactic acid, which gives the product its pleasant acid taste, a pH of 4.8, a high degree of aroma from diacetyl and slight effervescence from CO2 as well as a white color and smooth, thick body

On baking, the open crumb texture of the bread is result of the

Denatured bread proteins

What are microbial exopolysaccharides?

Different polysaccharides are used in food systems as stabilizers and texturizers. Lactic acid bacteria produce many different types of exopolysaccharides (EPS) that contain units of glucose, galactose, rhamnose, mannose, and other carbohydrates which are used to produce fermented dairy products with better consistency and texture (e.g. in yogurt and milk) & to hold moisture in low fat-high moisture cheeses (in mozzarella cheese). A wide range of microorganisms produce exopolysaccharides in the form of discrete capsules or as soluble slimes located outside the cell. They may protect the microorganism against desiccation, act as a barrier to viruses and chemical agents, aid attachment to surfaces, provide carbon and energy reserves.

Homolactic end products & enzymes

End products: 2 lactate Enzymes: Lactate dehydrogenase (Pyruvate reductase).

Heterolactic end products & enzymes

End products: Lactate, Ethanol, CO2 Enzymes: Pentose phosphate pathway

Describe the cheese production via microbial processes

First, raw milk is checked for various chemical and microbiological quality parameters and then pasteurized. The production of coagulated milk proteins or curd is then achieved by the activities of lactic acid bacteria. These bacteria have the ability to lower the pH through the fermentation of lactose to lactic acid, which facilitates protein coagulation. They also influence the flavor of the final product by producing specific flavor and aroma compounds. A mixed starter culture is often used, consisting of several strains of these mesophilic or thermophilic streptococci and lactobacilli, which may be prepared in heat-treated milk or whey-based media. Use of defined starter cultures reduces batch-to-batch variations in both production time and levels of acid generated. For some cheeses this may be further controlled by heat treatment at 55°C, which inhibits mesophiles and promotes the action of thermophiles (e.g. Streptococcus, Lactobacillus).

In sauerkraut production addition of salt help to reduce water activity inhibiting the growth of

Gram-negative bacteria

What are the superior qualities of milk used for fermentation of dairy products?

In fermented milk products, all the constituents of the milk are retained in the final products, with the exception of those partially metabolized by the bacteria. In cheeses, a large portion of milk constituents is removed to obtain the final products by evaporation of the whey (Whey or milk plasma) is the liquid remaining after milk has been curdled and strained) The growth of desirable microorganisms and the quality of a fermented dairy product are influenced by the composition of the milk used in a fermentation process

Describe mushroom farming

In specially constructed mushroom houses aseptically grown spawn is introduced into waste materials (e.g. lignocellulosic waste, sawdust, milled corn cobs) for the initial inoculum production The mycelium grows throughout the sawdust substrate and solidifies into "logs", which are subsequently taken out of the bags and placed on shelves in climate-controlled mushroom houses (solid state fermentation). Fruiting body formation is induced by temperature and humidity that differs according to species. The fruiting bodies are picked off by hand. The logs are usually soaked in water to replenish moisture and induced to form a new break, up to five or six times per log. Thereafter the spent log is discarded and the cycle is repeated. The mushroom houses have sophisticated temperature and humidity controls, and the air is filtered to control mould spores and diseases. Certain mushrooms and other fruiting bodies of filamentous fungi are edible and provide a good source of protein, whereas others have narcotic effects and some are highly toxic

Describe the microbially-mediated production of sauerkraut

In traditional processes natural microflora are used to perform fermentations. The prevailing conditions favor the sequential growth of lactic acid bacteria, especially Lactococcus species, along with Leuconostoc species, which tends to dominate the early fermentation until the acid level reaches 0.7-1.0% (v/v). At the later stages Lab. plantarum starts growing and brings the acid level to ca. 2%. Alternatively, a starter culture of suitable lactic acid bacteria can be added to perform the fermentation Nisin can be added to control the spoilage microorganisms (starter-cultures should be nisin-resistant) The characteristic of sauerkraut is the result of the combined effects of lactate, acetate, ethanol, CO2 and diacetyl in proper amounts Off-flavor, soft texture, and discoloration of sauerkraut can occur by growth of molds and yeasts when air is not completely excluded. A slimy texture of sauerkraut can occur due to overgrowth of Leuconostoc spp. In the presence of sucrose; they metabolize fructose but synthesize dextrans from glucose.

How is citrate transported and metabolized to produce diacetyl by some lactic acid bacteria?

Lac. lactis ssp. lactis biovar diacetylactis and Leuconostoc species can produce large amounts of diacetyl from citrate. Citrate, a 6C compound, is transported from the outside into the cells by the citrate-permease system. It is then metabolized through pyruvate to acetaldehyde ~ TPP (thiamin pyrophosphate). It then combines with pyruvate to form alpha-acetolactate, which is converted to diacetyl with the generation of CO2. Under a reduced condition, diacetyl can be converted to acetoin, with a loss of desirable flavor. A producer strain can also be genetically modified to produce excess diacetyl (metabolic engineering).

The characteristic of sauerkraut is the result of the combined effects of

Lactate, acetate, ethanol and diacetyl in proper amounts

The ropey, gelatinous consistency of viili is due to the actions of

Lactic acid bacteria and a yeast-like fungus

In yogurt production if the temperature is higher, which of the following bacterium predominates, causing more acid and less flavor production

Lactobacillus

In cocoa fermentation species of lactic acid bacteria are

Lactobacillus plantarum and fermentium

Microbial enzymes can be used to reduce food wastes and convert them into value added products such as

Methane

List the types of antimicrobial agents produced by the microorganisms

Microorganisms produce numerous antimicrobial agents, including organic acids, enzymes, & antibiotics.

What are the different types of food carbohydrates transported inside the lactic acid bacterial cells?

Monosaccharides and disaccharides are transported from the environment inside the cells either by the permease or PEP-PTS system. In food fermentation, they generally include several pentoses, glucose, fructose, sucrose, maltose, and lactose.

Describe the use of naringinase

Naringinase is a debittering enzyme that is used in the commercial production of citrus juices. It breaks down the compound naringin that gives citrus juices its bitter taste. It is a multienzyme complex which possesses alpha-L-rhamnosidase and beta glucosidase active centers.

Describe the use of natamycin

Natamycin is a polyene antifungal agent produced by Streptomyces species and is primarily approved as a surface antimycotic agent for food (e.g. cheeses). It is also used clinically for the treatment of fungal keratitis, and in treating cornea infections caused by species of Aspergillus and Fusarium

Describe the use of nisin

Nisin is very active against many Gram-positive bacteria, but alone has little or no effect on Gram-negative bacteria, yeasts or filamentous fungi. Its applications are mostly in controlling bacterial spoilage of both heat-processed and low-pH foods. These include dairy products, especially processed cheese, cheese spreads, egg products, dressings and sauces, along with several canned foods. It is particularly useful for controlling the outgrowth of endospores of bacilli and clostridia. Nisin is also very effective against Bacillus sporothermodurans, which is a thermophilic, heat-resistant, bacterium that can be a problem in ultra-high temperature (UHT) treated products. Other applications include the inhibition of spoilage bacteria during fermentation. Apart from food applications, nisin is used as sanitizer for the prevention of bovine mastitis in dairy cattle. More recently, its potential in controlling oral bacteria that cause mouth odor, plaque and gingivitis has been examined. Nisin also shows promise in skin-care products, as it is effective against Staphylococcus aureus and Staphylococcus pyogenes. A further therapeutic role is in the control of Helicobacter pylori, which infects the stomach mucosa and is associated with peptic ulcers.

What are nutraceuticals?

Nutraceuticals are products, which other than nutrition are also used as medicine. A nutraceutical product may be defined as a substance, which has physiological benefit or provides protection against chronic disease.

Heterolactic bacteria

One important heterolactic fermenter is Leuconostoc mesenteroides, which is used for souring vegetables like cucumbers and cabbage, producing pickles and sauerkraut, respectively. In hetero lactic fermentation, end product is ethanol and CO2 in addition to lactic acid. In this reaction glucose is first metabolized to pyruvate, acetic acid and CO2 by Pentose phosphate pathway. Pyruvate is then reduced to lactic acid whereas acetic acid is reduced to ethanol and CO2. Heterolactic bacteria: Leuconostoc mesenteroides, Lactobacillus bifermentans, Leuconostoc lactis

Bacterial blotch disease of mushrooms is caused by

Pseudomonas tolaasii

How are galactose, galactose-6-phosphate, and fructose metabolized by the EMP pathway by homolactic fermenters?

Other hexoses, such as fructose (transported as fructose or from hydrolysis of sucrose), galactose (from hydrolysis of lactose), and galactose-6-phosphate (from hydrolysis of lactose-phosphate following transport of lactose by the PEP-PTS system), undergo different molecular conversion before they can be metabolized in the EMP pathway. Thus, fructose is phosphorylated by ATP to fructose-6-phosphate before being used in the EMP pathway. Galactose is converted first to galactose-1-phosphate, then to glucose-1-phosphate, and finally to glucose-6-phosphate through the Leloir pathway before entering the EMP pathway. Galactose-6-phosphate is first converted to tagatose-6-phosphate, then to tagatose-1,6-diphosphate, and then hydrolyzed to dihydroacetone phosphate and glyceraldehyde-3-phosphate by the tagatose pathway before entering the EMP pathway.

Cultured buttermilk is produced via controlled fermentation by inoculating

Partially skim milk with a specific starter culture

Moromi is the second stage of soy sauce fermentation and involves an anaerobic fermentation of the liquid slurry that results from the addition of brine (sodium chloride solution) to koji. During this phase, the activities of which of the following bacterium acidify the environment and prevent spoilage

Pediococcus halophilus

Penicillium roquefortii

Penicillium roquefortii is used for ripening of Roquefort, Gorgonzola, and blue cheeses. Some strains can produce the neurotoxin roquefortin. In the selection and development of strains for use in cheese, this aspect needs careful consideration. Pen. camembertii is used in Camembert cheese and Pen. caseicolum is used in Brie cheese. They are also used to produce the enzyme glucose oxidase.

Curd formation might be promoted in unripened cheeses by addition of

Proteolytic enzymes

Most important enzyme used in cheese production is chymosin: an aspartic protease, which is also called

Rennin

Tempeh production involves fermentation of cooked whole or dehulled soya beans by

Rhizopus oligosporus

Rhizopus oryza

Rhizopus oryza is used to make tempe or temphe, murcha, chu, and nuruk.

During baking, molds are killed but spores can get in from air and equipment afterwards and grow inside within 1-2 days. The common black bread mold as an example can grow if moisture is released because of starch crystallization during storage. This mold is called

Rhizopus stolonifer

Brie is a

Ripened cheese

Discuss the production of Single Cell Proteins (SRPs) via microbial processes.

Single-cell proteins develop when microbes ferment waste materials (including wood, straw, cannery, and food-processing wastes, residues from alcohol production, hydrocarbons, or human and animal excreta). With 'electric food' processes the inputs are electricity, CO2 and trace minerals and chemicals such as fertiliser. The problem with extracting single-cell proteins from the wastes is the dilution and cost. They are found in very low concentrations, usually less than 5%. Engineers have developed ways to increase the concentrations including centrifugation, flotation, precipitation, coagulation, and filtration, or the use of semi-permeable membranes. The single-cell protein must be dehydrated to approximately 10% moisture content and/or acidified to aid in storage and prevent spoilage. The methods to increase the concentrations to adequate levels and the de-watering process require equipment that is expensive and not always suitable for small-scale operations. It is economically prudent to feed the product locally and soon after it is produced.

What are Single Cell Proteins (SRPs)?

Some microorganisms contain high levels of protein with good nutritional characteristics suitable for both human and animal consumption. This so-called single-cell protein (SCP) can be produced from a wide range of microorganisms cultivated on low-cost carbon sources. SCP is not a pure protein, but refers to the whole cells of bacteria, yeasts, filamentous fungi or algae, and also carbohydrates, lipids, nucleic acids, mineral salts and vitamins.

List three species from three genera that produce only l(+)-lactic acid from glucose.

Some of the species that produce l(+)-lactic acid (>90% or more) are Lactococcus lactis ssp. lactis and cremoris, Streptococcus thermophilus, Lactobacillus amylovorus, Lab. amylophilus, Lab. casei spp. casei, Lab. casei spp. rhamnosus, and Lab. divergens. Some of the common species used in food fermentation, namely Pediococcus acidilactici, Ped. pentosaceus, Lab. delbrueckii spp. bulgaricus and helveticus, Lab. acidophilus, Lab. reuteri, and Lab. plantarum, produce a mixture of d(-)- and l(+)-lactic acids with 20%-70% being l(+)-lactic acid.

Describe the fermentation process used for sausage production

Some processors now use controlled fermentation by directly inoculating commercial starter cultures, available as frozen or freeze-dried concentrates, in the meat mixture, rather than merely relying upon the natural indigenous microflora. The biological stabilization is achieved usually through the addition of salts and the generation of lactic acid by these bacteria (Pediococcus cerevisiae, Lactobacillus plantarum and Staphylococcus carnosus), which are tolerant to both salt and low water activity Over several days of fermentation and then weeks of ripening, the pH is reduced to around 5.0, and there are also changes in texture, flavor and color. Control of Clostridium botulinum is a major objective. Sodium and potassium nitrites and nitrates are used as curing agents in the meat. Reduction of added nitrate to nitrite may be enhanced by the nitrate reductase activity of certain strains of these micrococci. The mechanisms of antibacterial action of nitrite are not properly understood, but the inhibitory effect is probably produced in several ways, such as reactions with some enzymes in vegetative cells and germinating spores, restriction of the bacterial use of iron, and interference with membrane permeability, thereby limiting transport. In addition to clostridial species, nitrite is inhibitory, to some extent, to Staphylococcus aureus, Escherichia, Pseudomonas, and Enterobacter spp. However, in bacon, nitrite can lead to the formation of carcinogenic compounds such as nitrosamines. Because of this, there is a trend to reduce nitrite or to use other preservatives to control Clostridium botulinum in low-heat-processed meat products.

Fish fermentation is performed by the natural microflora that develops under specific conditions, mostly by the strains of

Staphylococcus carnosus and S. piscifermentans

Carbohydrates

Starch Glycogen (meat) Lactose (dairy) Sucrose Maltose Glucose Fructose Pentoses

Explain the functions of β-galactosidase and phospho-β-galactosidase.

Sucrose, maltose, and lactose, the three disaccharides, are hydrolyzed inside the cell by the enzymes sucrase, maltase, and lactase (β-galactosidase), respectively, to hexoses. Lactose~P (galactose-6-phosphate-glucose) is hydrolyzed by phospho-β- galactosidase to yield glucose and galactose-6-phosphate before further metabolism.

Describe the fermentation process used for fermented fish production

The fermentation is performed by the natural microflora that develops under these specific conditions, mostly strains of Staphylococcus carnosus and S. piscifermentans, which perform an effective reduction of nitrite and nitrate. The fermentation is generally a means of preservation, but can also improve digestibility, nutritional value, texture and flavor. S. carnosus strains are added as secondary flora for their beneficial effects on desired product color

Describe the three distinct stages of soya bean fermentations

The first stage koji is a solid substrate aerobic fermentation of cooked soya beans or steamed defatted soya flakes, along with wheat flour or rice. Normally, a mixture of strains of Aspergillus oryzae is used and at 25-30°C the hydrolysis of constituent starch by α-amylase, protein and pectins is accomplished in 2-3 days (Asp. oryzae is also used in the production of sake; and as a source of food enzymes). Moromi is the second stage and involves an anaerobic fermentation of the liquid slurry that results from the addition of brine (sodium chloride solution) to koji. During this phase, the activities of Pediococcus halophilus initially acidify and prevent spoilage Subsequently, in the final stage Candida species or Zygosaccharomyces rouxii (osmophilic yeast) perform an alcoholic fermentation and produce additional flavor compounds. The product is traditionally matured for 6-9 months to develop the full flavor before the liquid is filtered, pasteurized and finally bottled.

Discuss how lactic acid bacteria, while growing in milk, are able to transport lactose.

The high-energy phosphate from PEP is transferred sequentially to EnzI, HPr (both in the cytoplasm and nonspecific for lactose), FacIIILac, and EnzIILac (both on the membrane and specific for lactose), and finally to lactose. Lactose from the environment is transported in the cytoplasm as lactose-phosphate (galactose-6-phosphate-glucose). One molecule of lactose carries one H+ with it in the PermeaseLac molecule (specific for lactose). Once inside, there is a conformation change in the permease molecule, which causes release of the lactose molecule and H+ inside the cytoplasm. Release of lactose and H+ causes permease to change to the original conformation. Lactose is transported as lactose (galactose-glucose).

Describe the production of Xanthan gum.

The most commercially successful microbial exopolysaccharide is xanthan gum, produced by Xanthomonas species. These bacteria are small, motile, aerobic, Gram-negative rods producing yellow pigments. Surfactants produced by Xanthomonas campesteris are also widely used in petroleum recovery operations.

Describe the cacao fermentations

The pods of Theobroma cacao are opened and the material is removed by fermentation. Initially there is an alcoholic fermentation performed by a mixture of yeasts, notably Candida, Hansenula, Pichia and Saccharomyces. This is followed by an increase in the activity of lactic acid bacteria, particularly Lactobacillus plantarum and L. fermentum . Finally, acetic acid bacteria from the genera Acetobacter and Gluconobacter predominate and oxidize the ethanol to acetic acid. Ethanol, lactic acid, and acetic acid kill the beans and cause production of flavour precursors.

Describe how dairy waste could be treated via biological means

The possibility of using enzymes to reduce wastes and convert wastes to value added products is being explored. Lactose in whey has been treated with lactase (β-galactosidase) to produce glucose and galactose, which are then used in alcohol production by yeast or to produce baker's yeasts

Name two species of yeasts and briefly discuss the use of each in the production of fermented foods and food additives.

The process of making beer is called brewing. It includes breaking the starch in the grains into a sugary liquid, called wort, and fermenting the sugars in the wort into alcohol and carbon dioxide by yeasts. Two main species are used in the fermentation process: Saccharomyces cerevisiae (top-fermenting, since it forms foam on top of the wort) and Saccharomyces uvarum (bottom-fermenting). Top-fermenting yeasts are used to produce ale, while bottom-fermenting produce lagers. The temperature used for top-fermenting (15-24ºC) leads to the production of a lot of esters and flavor products that give beer a fruity taste. Hops are added to introduce a bitter taste and to serve as a preservative.

Describe the microbially-mediated production of bread

The rising of bread relies on the fact that wheat and several related cereal grains contain gluten protein. Glutens contribute to the final flavor of bread and have the characteristic of forming long molecular strings when they are "kneaded". These bind the bread together and have important elastic properties, allowing the formation of dough. Bread dough traps the carbon dioxide generated by the baker's yeast and rises due to the pressure of the carbon dioxide build-up The yeast also adds flavors, alcohol and acids. Importantly, it helps mature or chemically modify the gluten to promote even expansion of the dough and gas retention during baking. On baking, the bread protein is denatured and forms the open crumb texture. Also during baking, molds are killed but spores can get in from air and equipment afterwards and grow inside within 1-2 days. Some molds (Rhizopus stolonifer i.e. the common black bread mold) can grow if moisture is released because of starch crystallization during storage. Some frozen breads can also absorb moisture upon thawing enabling yeasts and bacteria to grow Acidification may be achieved by adding citric acid or by sour-dough fermentation; the latter also contributes additional flavor. The dough may be fermented by natural microflora of the dough ingredients. Initially, Gram-negative-enteric bacteria are involved, followed by lactic acid bacteria that reduce the pH. Alternatively, a portion of dough from a previous batch, predominantly containing a mixture of lactic acid bacteria, may be used as an inoculum. More recently, single strain commercial starter cultures of heterofermentative lactic acid bacteria have become available for this purpose.

In yogurt production initial milk inoculation involves a mixed starter culture containing thermophilic strains of Streptococcus thermophilus and Lactobacillus delbruckeii ssp. bulgaricus in a ratio of 1:1. The resulting protein-gel formation is achieved by these bacteria via production of

Their proteolytic enzymes and extracellular polymers

In pasteurized milk some of the bacteria can still grow and they are called

Thermoduric and pyschrotrophic bacteria

Semi-washed

This is a hybrid method of washed and natural, often referred to as wet- hulling. The cherries are pulped and rinsed. They do not go through a lengthy fermentation process. The parchment is removed while the beans are wet and soft due to the wet tropical climate producing low acid, heavy body, earthy and herbal flavours (Sumatra, Sulawesi).

List two species from two genera that produce diacetyl from citrate.

Two species are Lac. lactis ssp. Lactis biovar diacetylactis and Leuconostoc species that produce diacetyl from citrate. This type of fermentation is carried out by some lactic acid bacteria and some members of Enterobacteriaceae

Largest component of the milk composition is

Water

The liquid remaining after milk has been curdled and strained is called

Whey

Describe the yogurt production via microbial processes

Yoghurt has a sharp acid taste and the flavor is due to the combined effects of acetaldehyde, lactate, and acetate, but 90% of the flavor is due to acetaldehyde. While a continuous method has also been developed, yoghurt is generally fermented in batches. During batch fermentation the population of microorganisms goes through several distinct growth phases (e.g. lag, acceleration, exponential growth, decelerations, death). Inoculation involves a mixer starter culture containing thermophilic strains of Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus in a ratio of 1:1. The former produces mainly acid whereas the latter produces more organoleptic compounds like acetaldehyde. Their proteolytic enzymes and extracellular polymers also aid protein-gel formation. If the temperature is higher, Lactobacillus sp. predominates, causing more acid and less flavor production. At lower temperatures, growth of Streptococcus sp. is favored, forming a product containing less acid and more flavors. The two species show symbiotic growth while growing together in milk. Initially, Streptococcus sp. grows rapidly in the presence of dissolved oxygen and produces formic acid and CO2. The two species also have synergistic effect on the rate of growth, rate of acid production, and amounts of acetaldehyde formation when growing together as compared with when growing individually The major flavor component in yoghurt is acetaldehyde with some diacetyl and acetate. In plain yoghurt, if acetaldehyde concentration is too low, the flavor will be chalky and sour; if it is too high, it will give the yoghurt a green flavor. Similarly, too much diacetyl gives a buttery aroma. Also, too much acid production during storage causes a sour taste; and proteolysis and peptides will cause bitterness. Growth of yeasts during storage can produce a fruity flavor and longer storage may lead to molds on the surface.

NPN compounds

amino acids, urea, uric acid, creatine, and creatinine.

Cheese ripening involves modification of proteins and fats that remain in young cheese

by microbial and milk proteases and lipases

Mushroom production involves a(n)

controlled non-axenic solid-substrate fermentation

The rate of curing in cheese can be increased via the use of

enzymes obtained from cell lysates of starter-culture bacteria

Lactose in whey can be treated with

lactase (β-galactosidase) to produce glucose and galactose to be utilized by baker's yeast