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.
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Ancient fermented food processes, such as making bread, wine, cheese, curds, idli, dosa, etc., can be dated to more than 6,000 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.
There are 5 major groups of commercially important 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 |
| glycerol | |
| Starch | |
| Maltodextrine | |
| Lactose | milk whey |
| fats | vegetable oils |
| Hydrocarbons | petroleum fractions |
| Nitrogen | |
| Protein | soybean meal, corn steep liquor, distillers' solubles |
| Ammonia | pure ammonia or ammonium salts urea |
| Nitrate | nitrate salts |
| Phosphorus source | phosphate salts |
| Vitamins and growth factors | |
| Yeast, Yeast extract | |
| Wheat germ meal, cotton seed meal | |
| Beef extract | |
| Corn steep liquor | |
Trace elements: Fe, Zn, Cu, Mn, Mo, Co
Antifoaming agents : Esters, fatty acids, fats, silicones, sulphonates, polypropylene glycol
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.
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.
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.