Industrial fermentation

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Fermentation has many important uses in industry. Though the word fermentation can have stricter definitions, when speaking of it in industrial fermentation it more loosely refers to the breakdown of organic substances and re-assembly into other substances. Somewhat paradoxically, fermenter culture in industrial capacity often refers to highly oxygenated and aerobic growth conditions, whereas fermentation in the biochemical context is a strictly anaerobic process.

Food fermentation

Ancient fermented food processes, such as making bread, wine, cheese, curds, idli, dosa, etc., can be dated to more than 6,000 yr ago. They were developed long before man had any knowledge of the existence of the microorganisms involved. Also, fermentation is 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:

  1. Microbial cells or biomass as the product, e.g. bakers yeast, lactobacillus, etc.
  2. Microbial enzymes: catalase, amylase, protease, pectinase, glucose isomerase, cellulase, hemicellulase, lipase, lactase, streptokinase, etc.
  3. Microbial metabolites :
    1. Primary metabolites – ethanol, citric acid, glutamic acid, lysine, vitamins, polysaccharides etc.
    2. Secondary metabolites: all antibiotic fermentation
  4. Recombinant products: insulin, HBV, interferon, GCSF, streptokinase
  5. Biotransformations: phenyl acetyl carbinol, 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

Nutrient Raw material
Carbon
Glucose corn sugar, starch, cellulose
Sucrose sugarcane, sugar beet molasses
Lactose milk whey
Fats vegetable oils
Hydrocarbons petroleum fractions
Nitrogen
Protein soybean meal, cornsteep liquor, distillers' solubles
Ammonia pure ammonia or ammonium salts
urea
Nitrate nitrate salts
Phosphorus source phosphate salts

Trace elements: Fe, Zn, Cu, Mn, Mo, Co

Antifoaming agents : Esters, fatty acids, silicones, sulphonates, polypropylene

Buffers: Calcium carbonate, phosphates

Growth factors: Some microorganisms cannot synthesize the required cell components themselves and need to be supplemented, e.g. with thiamine, biotin, calcium pentothenate

Precursors: Directly incorporated into the desired product: Phenyl ethylamine into Benzyl penicillin, Phenyl acetic acid into Penicillin G

Inhibitors: To get the specific products: e.g. sodium barbital for rifamycin

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,olive oil and tween are also used at times.

Chelators: Chelators are the chemicals used to avoid the precipitation of metal ions. Chelators like EDTA, citric acid, polyphosphates are used in low concentrations.

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 fertilisers. Digested solids, known also as sludge, is dried and used as fertilisers. Gaseous by-products such as methane, can be utilised 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

External links

Related journals


References

  • Schuytser, M.A.I., 2003, Solid state fermentation, PhD Thesis, Wageningen UR
  • Biochemical Engineering Fundamentals by J.E. Bailey and P.F. Ollis, McGraw Hill Publication
  • Principles of fermentation technology by Stansbury, P.F., A. Whitaker and S.J. Hall, 1997

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