Microorganism is used to produce products such as antibiotics and amino acids in large quantity. These products have changed our lives and also increased our life span. Microorganisms are also used to produce products such as food additives, biofuels, industrial products, agricultural products and also pharmaceutical products for human as well as animal health. In recent times industrial microbiology techniques are used to produce nonantibiotic compounds that can be used as medicine to improve well-being of both human and animal population.
Industrial microbiology techniques are used to produce many antibiotics produced by microorganisms mainly by actinomycetes belongs to the genus Streptomyces and also filamentous fungi. Synthesis of the several of the most important antibiotics such as penicillin and streptomycin are discussed along with the importance of media formulation and also environmental influence on the production of these antibiotics.
Antibiotic penicillin is produced by Penicillium chrysogenum in large quantities. Production of penicillin requires precise adjustment of the culture media composition to achieve maximum yield. Rapid cell division can be achieved by adding high level of glucose as carbon source, but this will not yield high antibiotics. But by using slowly hydrolyzed disaccharide lactose, in addition with limited nitrogen leads to high production of antibiotic penicillin after growth has stopped. Same kind of yield can also be achieved by using a slow and continuous feed of glucose as carbon source. To get a particular type of antibiotic penicillin specific precursors are added to the culture media. For example antibiotic penicillin G, which has got a benzyl side chain, can be produced in large quantity using precursor phenyl acetic acid. The pH of the fermentation medium is maintained at around neutral by adding sterile alkali. This neutral pH provides maximum stability to the newly synthesized antibiotic penicillin. Usually fermentation completes in six to seven days, then the broth is separated from the fungal mycelium cells and antibiotic is downstream processed using techniques such as absorption, precipitation and crystallization to get final pure form of penicillin. This penicillin is then undergoes some chemical procedures to get a variety of semi synthetic antibiotic penicillin.
Streptomycin is produced by Streptomyces griseus, as secondary metabolite. Streptomycin production or accumulation is influenced by the changes in environmental condition and also substrate availability. For this fermentation process soybean-based medium along with glucose is used as carbon source. That is nitrogen source is provided in this combined form or soybean meal form, this also acts as growth limiting factor. After the initial growth, antibiotic production and also accumulation increases in the fermentation medium.
Amino acid production in industrial scale is produced using regulatory mutants, which have a reduced ability to limit synthesis of end product. As the normal microorganisms limits the overproduction of biochemical intermediates such as amino acid by regulating the cellular mechanisms. Amino acids like lysine and glutamic acid are widely used as nutritional supplements in the food industry, such as in bread products and also as flavour-enhancing compound known as monosodium glutamate.
Glutamic acid production is done in large quantity by using mutant strain of Corynebacterium glutamicum that lack or have limited ability to convert ketoglutarate to succinyl-CoA in TCA cycle. Fermentation medium with low biotin and addition of fatty acid derivatives increases membrane permeability; this in turn increases the excretion of glutamic acid. Production and also accumulation of glutamic acid increases after the completion of initial growth phase.
Lysine is an essential amino acid; therefore it is used as supplements in cereals and also in bread products. Lysine was initially produced in a two step process but now it is done using single-step fermentation process. Lysine is produced in large quantity by using bacterium Corynebacterium glutamicum, by blocking the homoserine synthesis; this in turn increases the accumulation of lysine. In a three day fermentation around 44g/liter lysine can be produced using these bacteria.
Microorganisms can be used to produce a large quantity of industrially important products such as antibiotics and amino acids. The field of antibiotic and amino acid production is expanding continuously. Research is being conducted to improve and discover new ways to produce these biologically important compounds. For example around 300 new antibiotics are being discovered every year.
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