Last revised: Monday, May 5, 2003
Reading: Ch. 31 and 32 in text
Industrial Microbiology
History
- Microbial activities have been important ever since the discovery of fermentations. Beer & wine, leavened bread were important commerical products even in early Sumerian cultures (4th century B.C.)
- Industrial microbiology came of age in the 20th century. Until development of cheap oil, fermentations were used not only for food and beverages, but to make acetone, butanol, and ethanol on large scale.
- With rise of biotechnology in last half of 20th century, ability to genetically modify microbes to produce desired products as grown enormously.
- Most industrial processes use large fermentation vessels (fermenters), can hold 1000's to hundreds of thousands of liters. A single large scale fermeter can 200,000 liters!
- Photograph of brewery fermenter
- Photograph of industrial fermenter tanks
- Schematic diagram of industrial fermenter
- Primary and Secondary Metabolites
- Many commercially desirable microbial products are not produced during logarithmic (primary) growth, but instead are produced as cells enter stationary phase (secondary growth). Such products are called secondary metabolites
- Example: View diagram showing when penicillin is produced in fungal culture relative to fungal growth.
- Secondary metabolites include antibiotics.
- Antibiotics. Over 10,000 different antibiotics have been isolated and characterized. About 160 are produced in commercial quantities. Pfizer is one of Connecticut's largest companies, a major antibiotic producer.
- Biocides. Example: Bacillus thuringiensis produces crystalline material that destroys insect guts of lepidopterans (caterpillars), very effect and specific pesticide.
- Foods produced by fermentation. Includes cheeses, fermented milk products (yogurt, sour cream, buttermilk, etc.), leavened breads, saurkraut, pickles, soy sauce, more.
- Beverages produced by fermentation . Includes wine, beer and ale, fermented grain mashes used to produce all distilled liquors.
- Foods and flavoring agents. Includes mushrooms, yeast cells, vinegar, nucleotides, amino acids, vitamins, organic acids.
- Enzymes. Over 500 tons of purified enzymes are produced annually, enormous commercial value. Include proteases (used in detergents), amylases (used in production of syrup, brewing, baking, animal feed, detergents), rennin (used in cheese making), Taq polymerase (used in PCR).
Environmental Microbiology
Introduction
- Microbes are nature's decomposers. The variety of metabolic abilities in microbes is enormous, and includes microbes that can degrade or mitigate all sorts of human products and activities, from oil spills to pesticide runoff to toxic waste.
- Environmental Microbiology seeks to find ways to maximize the efficiency of microbes in helping to remove various kinds of wastes (e.g. sewage treatment), or to minimize the opportunities of microbes to produce problems (e.g. water treatment).
- Environmental Microbiology is a growing field, often brings together issues of concern to engineers, geologists and hydrologists, microbiologists, and public health officials.
- Until 1900's, human wastes were simply dumped as raw sewage into the nearest outhouse, stream, or river. As connection of sewage to diseases such as cholera became clear, public policy changed to required water treatment. This had major impact on reduction of many diseases.
- Sewage = mix of domestic + industrial waste plus drainage water from rainfall. Contains many microbes, mostly harmless but some pathogens from humans or animals. Can include bacteria such as Vibrio cholera, Shigella dysenteriae, enteropathogenic strains of E. coli and B. cereus, viruses such as Hepatitis A, many more.
- Sewage treatment: goal is to get rid of pathogens, also reduce organic content of effluent to a low level.
- Primary wastewater treatment: use screens to remove large objects (plastic bags, wads of paper, etc.), then move water to large tank to allow settling of heavier particulate matter as sludge.
- Secondary wastewater treatment: modern facilities use "activated sludge process". After moving water from primary settling tank, bubble air through a secondary tank. Aerobic microbes grow and break down organic matter in the tank. Then move water to another tank called the secondary clarifier, where solids settle and are added to sludge. Clarified liquid is treated with chlorine to kill remaining microbes, then discharged as clear liquid into nearest river.
View diagram of "active sludge" process
Note that sludge can be further broken down in anaerobic sludge digestor. Anaerobic bacteria break down organic matter, produce lots of fermentation products. Methanogens grow on these wastes and produce methane gas as waste. This can be trapped and used as fuel (useful in developing countries). - Tertiary wastewater treatment: Secondary wastewater treatment does not remove inorganic ions, such as NH3, PO4-3, SO4-2. Wastewater can enrich local waters to create eutrophic conditions, including algal blooms and sufficient loss of oxygen that fish die. To prevent this, a few water treatment systems use additional steps to remove ammonia and phosphate, using additional processing tanks in which specific bacteria are used to remove ammonia and phosphate.
- Expanded use of chemicals in industry has produced major new problems of environmental pollution. U.S. alone has over 50,000 hazardous waste sites. Entire communities have been evacuated because of accumulated toxic wastes. Groundwaters are often polluted as well, including toxic chemicals such as commercial solvents used to degrease machinery or in "dry cleaning". Fertilizers and pesticides are often found in water downstream from agriculture.
- Bioremediation = use of living organisms to promote destruction of environmental pollutants. See example of anaerobic toluene degrader .
- Typically, native microbes are used (rather than introduced or genetically mofified organisms). Rather than waiting for "nature to take its course", try to speed up the process. How?
- "Pump and treat". One way to speed bioremediation. Pump groundwater to surface, add nutrients (e.g., O2, methane), reinject into contaminated zone. In some cases, can inject
- Bioreactor. Another technique. Put contaminated soil or groundwater into an industrial-sized fermentor, add appropriate microbes to degrade materials, keep adding more substrate over time. This works well for very toxic chemicals such as chlorinated compounds (PCBs).
- Example: View chart showing dechlorination of a pollutant (in green) by bioremediation. How long does the process take?