I. Applied microbiology (Chapter 26) A. The capabilities of individual microorganisms or microbial ecosystems can be exploited for specific purposues

Transcription

1 I. Applied microbiology (Chapter 26) A. The capabilities of individual microorganisms or microbial ecosystems can be exploited for specific purposues 1. industrial microbiology = use of microorganisms to produce cells, specific products, or to perform a specific process a. organic chemicals (solvents, feedstocks), enzymes, antibiotics, hormones, steroids, foods, etc. b. sewage treatment, control of insects, recovery of metals, various environmental uses, including bioremediation 2. biotechnology = generally implies use of recombinant DNA techniques to design proteins or modify gene expression a. originally strains were selected and improved crudely, at most using non-specific mutagenesis b. modern methods allow recombination using markedly different organisms (1) insertion of specific genes to provide new capabilities (2) trangenics B. industrial fermentation = large scale cultivation of microorganisms 1. primary metabolite = produced during growth phase and normally involved in synthesis of new cells a. amino acids b. nucleotides c. fermentation endproducts d. enzymes e. cofactors 2. secondary metabolite = usually accumulate after the active growth phase and have no direct relationship to synthesis of cell material or normal growth a. antibiotics b. mycotoxins C. recombinant DNA technology 1. strains often include biological markers to allow easy identification of mutants a. nutritional requirements b. antibiotic resistance 2. protein engineering = modification of a protein molecule to enhance functioning 3. metabolic engineering = restructuring of metabolic networks by introduction of proteins fro m other cells a. allows synthesis of entirely new products and intermediates b. products include synthetic medical peptides that promote wound healing and blood coagulation, treat cancer or AIDS, influence sexual dysfunctions, help hormonal disorders c. major advantage of biological synthesis is production of specific stereoisomers (e.g., thalidomide) D. biocontrol of pests 1. Bacillus thuringiensis produces an intracellular protein toxin crystal that acts as an insecticide a. crystal is solubilized only by insects with high ph in midgut

2 b. fermentor technology allows accumulation of toxin for solubilization prior to large-scale distribution c. current efforts directed towards production of toxin using plasmid-coded genes 2. viruses that are pathogenic for specific insects (usually butterflies and moths) have been produced commercially E. biopolymers (gums) have been produced and used as additives in pharmaceuticals and foods (stabilization, water retention, flow characteristics, film-forming) 1. production not subject to climatic, political, or economic constraints 2. production facilities can be located near sources of inexpensive substrates (or endusers) F. biosensors can use living microorganisms or active enzymes t o measure specific components 1. enzyme (or metabolic) activity used to generate electrical impulse 2. impulse related to presence of specific compounds, even in highly mixed or "dirty" environments 3. replacing and expanding applications of bioassays a. food components (alcohol) b. pollutants c. toxic gases d. direct measurement of flavors, essences, and pheromones G. biodeterioration can be a problem (e.g., spoilage or corrosion) or beneficial (bioremediation) 1. fuels a. usually occurs at water/hydrocarbon interface b. can be detrimental (1) oil souring (2) jet fuel deterioration by Cladosporium resinae c. can be applied to bioremediation of oil spills (1) 1st form of bacterial life patented (Pseudomonas) (2) oleophilic fertilizers (3) application of specific organisms or communities 2. paper/cellulosic materials a. microbes can lower process efficiency by growing in treatment solutions b. mercury compounds often used as biocides, being replaced by chlorine, phenols, and organosulfides c. waste streams can be bioprocessed for cleanup d. cellulose (most plentiful organic compound on earth) can be the feedstock for microbial production of chemicals, including fuels 3. metals a. corrosion, especially anaerobically, is a major problem b. Thiobacillus ferrooxidans can leach up to 70% of copper content from lowgrade ores, aiding in recovery 4. textiles and leather a. common in high humidity or tropical areas b. controlled with phenols and copper compounds

3 II. 5. paints a. control methods use to include addition of mercury compounds b. currently use copper compounds (especially marine applications) and quartenary amines Industrial microbiology A. Three primary areas 1. produce cells as the desired product a. yeast for food b. lactic acid for probiotics c. cells to be used for other processes (1) biological warfare (2) bioremediation 2. use cells to carry out a process a. modify molecules from one form to another b. bioremediation (breakdown of pollutants) 3. microbial products a. alcohol b. antibiotics c. enzymes III. Food production A. Microbially-based foods are as old as civilization 1. preservation: activity by one group of microorganisms can prevent the growth of pathogenic bacteria 2. enhancement: microbial activity can produce or improve foo dstuffs 3. the most important microbes have been the lactic acid bacteria and yeasts, particularly Saccharomyces cerevisiae 4. encompasses all three areas of industrial microbiology B. lactic acid bacteria (LAB) preserve food by lowering the ph 1. strictly fermentative, aerotolerant anaerobes 2. vegetables (sauerkraut, kim chee, etc.) 3. dairy (yogurt, cheese, kefir, etc.) 4. meat (summer sausage, salami) 5. grain (sourdough starter) 6. probiotics C. Saccharomyces cerevisiae 1. ferments glucose to ethanol plus carbon dioxide a. doesn t hydrolyze starch b. facultative anaerobe 2. used to make bread and fermented beverages (e.g., wine, beer) a. grapes contain sugar and can be directly fermented b. grains (e.g., barley) contain starch that must be hydrolyzed to glucose (1) starch is convert ed to glucose by amylase (2) common sources of amylase are germinating seeds (malting) and saliva 3. other yeasts (e.g., Pichia pastoris) can be used as single cell protein (SCP) D. Many other foods are made or modified by microbes

4 1. soy sauce (Aspergillus oryzae) 2. aged meat 3. vinegar (Acetobacter acetii) 4. chocolate (yeasts, LAB, acetic acid bacteria) 5. tempe (Rhizopus) E. Food spoilage 1. transformation can be detrimental a. tastes ruined b. disease transmission c. toxins 2. environmental factors influence the ease of food spoilage a. ph influences microbial population (1) low ph favors growth of yeasts and molds (2) at neutral or alkaline ph, bacteria are more dominant (3) putrefaction = anaerobic breakdown of proteins, releasing foul-smelling amine compounds (4) common with meats b. water availability (dehydration) can be used to preserve food c. oxidation-reduction potential influences spoilage (1) cooked meat or broths have low redox potentials, ideal for growth of clostridia (2) anaerobes grow for long periods in sealed containers d. physical structure influences spoilage (1) sausage and hamburger have increased surface area and grinding spreads bacteria throughout the food (2) fruits and vegetables have protective skins, although spoilage microorganisms have enzymes that allow penetration of peels and rinds e. many foods contain natural antimicrobials (1) aldehydes and phenolics in cinnamon, mustard, and oregano (2) coumarins in fruits and vegetables (3) lysozyme in cow's milk and eggs f. plastic films (shrink-wrapped foods) allows penetration of oxygen (1) increased surface growth of bacteria (2) excess CO 2 lowers ph, selects for lactobacilli 3. approaches to food preservation a. physical removal (filtered beer) b. temperature (1) refrigeration retards microbial growth (a) (b) selects for psychrophiles and psychrotrophs microbial growth reported at -10 o C in fruit juice concentrates, ice cream, some fruits (2) pasteurization reduces microbial populations (3) canning sterilizes food c. chemical additives are used as preservatives (1) organic acids, sulfite, ethylene oxide, sodium nitrite, ethyl formate

5 (2) organic acids work best at low ph (undissociated) (3) nitrites prevent germination of clostridial spores (a) preserve red color in meat (b) can form carcinogenic nitrosamines d. gamma irradiation works well with moist foods because the process produces peroxides in cells, disrupting cellular components 4. Food poisoning a. food-borne infection = ingestion of pathogen, followed by growth accompanied by tissue invasion and/or release of toxins in the host intestine IV. Industrial fermentations A. Performed (usually) in large culture vessels in batch or continuous culture 1. batch cultures are more common a. simpler b. necessary for certain processes (1) foodstuffs (e.g., cheese, fermented beverages) (2) production of secondary metabolites 2. continuous culture can be more economical but much more complicated to operate over time B. Microbial products 1. pharmaceuticals a. antibiotics b. vaccines c. drugs d. may use natural or engineered strains 2. organic commodity chemicals a. glycerol b. solvents (e.g., ethanol, acetone, butanol) c. acetic acid 3. food supplements a. vitamins b. amino acids c. the cells themselves (SCP) 4. enzymes a. most involve natural organisms but genetic engineering is making inroads b. proteases, lipases, cellulases, amylase, etc. C. Other areas of applied microbiology 1. bioconversions = using cells or enzymes to synthesize complex chemicals, like hormones 2. bioremediation = using organisms to degrade pollutants a. organic waste treatment (sewage) b. oil spills c. chemical spills or leaks d. heavy metals e. clean up of industrial wastes (liquid and gas) f. usually applied to prevent or remove contamination of water systems

6 3. biohydrometalurgy = recovery of metals from low-grade ores a. chemolithotrophs use sulfides in ore as an energy source (1) sulfides are normally complexed with metals (2) removal of sulfide by the organism releases the metals b. applied to copper and iron c. mobilization of toxic metals, like arsenic, are being studied