Industrial fermentation
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The use of fermentation is an important process in the industry. Though fermentation can have stricter definitions, when speaking of it in Industrial fermentation, it more loosely refers to the breakdown of organic substances and re-assembley 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.
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[edit] Food fermentations
Ancient fermented food processes, such as making bread, wine, cheese, curds, idli, dosa, etc., some of which are some 6,000 yearr old, and developed long before man had any knowledge of the existence of the micro-organisms involved. Also, fermentation is a powerful weapon for semi-industrialized countries like Honduras, in their willingness to produce bio-diesel.
[edit] Cheese Making
Pasteurised milk is fermented by the bacteria, Lactobacillus sp., which work best at 40 degrees Celsius. Lactobacillus works on lactose in milk to coagulate/curdle forming curds. The enzyme rennin is added to milk together with bacteria to cause the milk to coagulate more than it would with just the bacteria. The curds and fats are then separated from the liquid part of the milk and are pressed to form cheese. After curdling, the liquid part of the milk (whey) is removed and used for making sweets for animal feeds. Different kinds of cheese are made using different types of milk and different mixtures of bacteria, (e.g. Streptococcus sp.) working at different temperatures.
Flavouring and variations:
Salt can be added Fungal spores (e.g. Penicillium can be added to give flavor and blue streaks like in blue Stilton cheese) Large holes in cheese are made by carbon dioxide produced by bacteria (Emmenthal cheese)
[edit] 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.
[edit] 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.
