Foundations in Microbiology

Seventh Editionss

Chapter 27

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27.1 Applied Microbiology and Biotechnology

• Applied microbiology – microbes are used to treat wastewater and bioremediate damaged environments

• Industrial microbiology – use of microbes in making food, medical, manufacturing, and agricultural products

• Biotechnology – uses microbes for practical applications

• Fermentation – controlled culture of microbes to produce desired organic compounds

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Water and Wastewater Treatment

Water purification• In most cities, water is treated in a stepwise process

before it is supplied to consumers• Impoundment in large, protected reservoir – storage

and sedimentation; treated to prevent overgrowth of cyanobacteria

• Pumped to holding tanks for further settling, aeration, and filtration; chemical treatment with a chlorine, ozone, or peroxide disinfectant

Figure 27.1 Major steps in water purification

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Sewage treatment• Sewage – used wastewater containing chemicals,

debris, and microorganisms• Typically requires 3 phases:

– Primary phase – removes floating, bulky physical objects

– Secondary phase – removes the organic matter by biodegradation, natural bioremediation in a large digester forming sludge which is aerated by injection and stirred

– Tertiary phase – filtration, disinfection, and removal of chemical pollutants

• Gradually released• Anaerobic digesters: turn sludge into a secondary

source of energy

Figure 27.3 The primary, secondary, and tertiary stages in sewage treatment

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Insert figure 26.24Sewage treatment

Figure 27.4 Treatment of sewage and wastewater

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27.2 Microorganisms and Food

• Microbes and humans compete for nutrients in food

• The effects of microorganisms on food can be– Beneficial– Detrimental– Neutral

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Microbial Fermentations in Food Products

Microbes, through fermentation, can impart desirable aroma, flavor, or texture to foods (starter cultures)

• Bread – yeast leaven dough by giving off CO2

• Beer – fermentation of wort• Wine – fermentation of fruit juices• Vegetable products – sauerkraut, pickles• Vinegar – fermentation of plant juices• Milk and dairy products – cheeses, yogurt

Figure 27.5 Hops

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Figure 27.7

Wine making

Figure 27.8 Microbes at work in milk products

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Figure 27.9 Cheese making

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Microorganisms as food

• Mass-produced yeasts, molds, algae, and bacteria

• Single-celled protein and filamentous mycoprotein added to animal feeds

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Microbial Involvement in Food-Borne Diseases

• Food poisoning – diseases caused by ingesting food

• 2 types:– Food intoxication – results from ingesting exotoxins

secreted from bacterial cells growing in food– Food infection – ingestion of whole microbes that

target the intestine – salmonellosis, shigellosis

• Other common agents – Campylobacter, Salmonella, Clostridium, Shigella, Staphylococcus aureus

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Insert figure 26.31Food-borne illnesses

Figure 27.10 Food-borne illnesses

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Prevention Measures for Food Poisoning and Spoilage

• Prevent incorporation of microbes into food– Aseptic technique– Handwashing and proper hygiene

• Prevent survival or multiplication of microbes in food– Heat – autoclaving, pasteurization, cooking– Cold – refrigeration, freezing– Radiation – UV, ionizing– Chemical preservatives – NaCl, organic acids– Dessication– Spraying of bacteriophages

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Figure 27.11 Preventing food poisoning and

spoilage

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Figure 27.12 Pasteurizer

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Figure 27.13 Temperatures and microbial

growth

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27.3 General Concepts in Industrial Microbiology

• Bulk production of organic compounds such as antibiotics, hormones, vitamins, acids, solvents, and enzymes

• Many processes involving fermentation

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• Mutant strains of bacteria and fungi that synthesize large amounts of metabolic intermediates (metabolites)

• Primary metabolites – produced during major metabolic pathways and are essential to microbe’s function – Amino acids, organic acids synthesized during logarithmic

growth

• Secondary metabolites – by-products of metabolism that may not be critical to microbe’s function – Vitamins, antibiotics, and steroids synthesized during

stationary phase

Figure 27.14 Primary and secondary microbial metabolites harvested by industrial

processes

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Tricks to Increase the Amount of Chosen End Product

1. Manipulate growth environment to increase synthesis of metabolite

2. Select strains that genetically lack a feedback system

3. Many syntheses occur in sequential fashion involving more than one organism

– Biotransformation – waste product of one organism becomes the building block of the next

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Figure 27.15 Example of biotransformation

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From Microbial Factories to Industrial Factories

• Produce appropriate levels of growth and fermentation in a carefully controlled environment

• Commercial fermentation carried out in fermentors – a device in which mass cultures are grown, reactions take place, and product develops

Figure 27.17

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Substance Production

• Steps in mass production:1. Introduction of microbes and sterile media into

reaction chamber2. Fermentation3. Downstream processing (recovery, purification,

packaging)4. Removal of waste

• Carried out aseptically and monitored for rate of flow and quality of product

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Figure 27.18Layout for a fermentation plant

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• Batch fermentations – substrate added to system all at once and taken through a limited run until product is harvested

• Continuous feed systems – nutrients are continuously fed into the reactor and product is siphoned off throughout run

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• Pharmaceutical products– Antibiotics– Hormones– Vitamins– Vaccines

• Miscellaneous products– Biopesticides– Enzymes– Amino acids– Organic acids– Solvents– Natural flavor compounds