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Industrial fermentation is the intentional use of fermentation by microorganisms such as bacteria and fungi to make products useful to humans. Fermented products have applications as food as well as in general industry.
Food fermentation 
Ancient fermented food processes, such as making bread, wine, cheese, curds, idli, dosa, etc., can be dated to more than seven thousand years ago. They were developed long before man had any knowledge of the existence of the microorganisms involved. Fermentation is also a powerful economic incentive for semi-industrialized countries, in their willingness to produce bio-ethanol.
Pharmaceuticals and the biotechnology industry 
There are 5 major groups of commercially important fermentation:
- Microbial cells or biomass as the product, e.g. single cell protein, bakers yeast, lactobacillus, E. coli, etc.
- Microbial enzymes: catalase, amylase, protease, pectinase, glucose isomerase, cellulase, hemicellulase, lipase, lactase, streptokinase, etc.
- Microbial metabolites :
- Recombinant products: insulin, hepatitis B vaccine, interferon, granulocyte colony-stimulating factor, streptokinase
- Biotransformations: phenylacetylcarbinol, steroid biotransformation, etc.
Nutrient sources for industrial fermentation 
Growth media are required for industrial fermentation, since any microbe requires water, (oxygen), an energy source, a carbon source, a nitrogen source and micronutrients for growth.
Carbon & energy source + nitrogen source + O2 + other requirements → Biomass + Product + byproducts + CO2 + H2O + heat
|Glucose||corn sugar, starch, cellulose|
|Sucrose||sugarcane, sugar beet molasses|
|Protein||soybean meal, corn steep liquor, distillers' solubles|
|Ammonia||pure ammonia or ammonium salts
|Phosphorus source||phosphate salts|
|Vitamins and growth factors|
|Yeast, Yeast extract|
|Wheat germ meal, cotton seed meal|
|Corn steep liquor|
Trace elements: Fe, Zn, Cu, Mn, Mo, Co
Buffers: Calcium carbonate, phosphates
Inducers: The majority of the enzymes used in industrial fermentation are inducible and are synthesized in response of inducers: e.g. starch for amylases, maltose for pollulanase, pectin for pectinase.
Sewage disposal 
In the process of sewage disposal, sewage is digested by enzymes secreted by bacteria. Solid organic matters are broken down into harmless, soluble substances and carbon dioxide. Liquids that result are disinfected to remove pathogens before being discharged into rivers or the sea or can be used as liquid fertilizers. Digested solids, known also as sludge, is dried and used as fertilizer. Gaseous byproducts such as methane can be utilized as biogas to fuel generators. One advantage of bacterial digestion is that it reduces the bulk and odour of sewage, thus reducing space needed for dumping, on the other hand, a major disadvantage of bacterial digestion in sewage disposal is that it is a very slow process.
Phases of microbial growth 
When a particular organism is introduced into a selected growth medium, the medium is inoculated with the particular organism. Growth of the inoculum does not occur immediately, but takes a little while. This is the period of adaptation, called the lag phase. Following the lag phase, the rate of growth of the organism steadily increases, for a certain period--this period is the log or exponential phase. After a certain time of exponential phase, the rate of growth slows down, due to the continuously falling concentrations of nutrients and/or a continuously increasing (accumulating) concentrations of toxic substances. This phase, where the increase of the rate of growth is checked, is the deceleration phase. After the deceleration phase, growth ceases and the culture enters a stationary phase or a steady state. The biomass remains constant, except when certain accumulated chemicals in the culture lyse the cells (chemolysis). Unless other micro-organisms contaminate the culture, the chemical constitution remains unchanged. Mutation of the organism in the culture can also be a source of contamination, called internal contamination.
See also 
||This article includes a list of references, related reading or external links, but its sources remain unclear because it lacks inline citations. (April 2012)|
- Biochemical Engineering Fundamentals, J.E. Bailey and P.F. Ollis, McGraw Hill Publication
- Principles of Fermentation Technology, Stansbury, P.F., A. Whitaker and S.J. Hall, 1997
- Penicillin: A Paradigm for Biotechnology, Richard I Mateles, ISBN 1-891545-01-9