Write an essay on the industrial importance of Bacteria.

Ans. Although the bacteria are known as great enemy due to their large number of harmful activities, yet there are also several useful activities which gives us relief and comforts to a greater extent. A number of free living bacteria give significant biochemical products essential for human consumption. In fact, they are master chemist causing remarkable transformations. In the industrial field they play important role resulting in several essential products. Following are the industrial products produced by bacteria :

1. Manufacture of Vinegar : The name vinegar literally signifies ‘sour wine’ in French. When wine or beer is exposed to air, it frequently turns sour because of oxidation of alcohol to acetic acid by aerobic acetic acid bacteria. On industrial scale the bacteria Acetobacteraceti are allowed to grow on alcohol in wooden vats or casks where they bring about slow oxidation to yield vinegar. In this process 10% alcohol is converted to 90% acetic acid within 4-5 days. This vinegar is clarified by filtration, pasteurization and bottled.

2. Dairy Products: Preparation of many fermented products of milk, like butter, cheese and yogurt etc. is based on the activities of bacteria, especially lactic acid bacteria.

In the manufacturing of cheese, bacteria help in curdling and ripening. Lactic acid produced by lactic acid bacteria lowers the pH considerably and helps in coagulation of milk protein (casein). This process is called curdling. Ripening of curd imparts characteristic flavour depending upon the type of cheese. In American cheese this is brought about by lactic acid bacteria whereas in Swiss cheese this role is played by propionic acid bacteria.

Butter is made by churning the cream that has been sourced by lactic acid bacteria. Lactic acid is produced by Streptococcus lactis whereas Leuconostoc citrovcrum imparts the flavour.

3. Dextran Production : Some lactic acid bacteria like Leuconostoc are capable of producing dextran (an extracellular polysaccharide) from sucrose. Dextran is used as a partial substitute of blood plasma. It is also used as a stabilizer in food products. In Biological research dextran derivatives, under the name sephadex is used as a sieve for the separation of macromolecules and in determining their molecular weight.

4. Acetone-Butanol Industry: Acetone-butanol fermentation is one of the oldest fermentation known. The butyric acid bacteria ferment sugars under anaerobic conditions, to carbon dioxide, hydrogen, butanol and acetone. Clostridium acetobutylicum is the organism of choice in the production of these organic solvents. Both acetone and butanol find a variety of industrial uses.

5. Butylene Glycol : This material is used in the manufacture of synthetic rubber and various other polymers. The bacterium Aerobacter is responsible for producing acetylmethyl carbinol (acetoic) which is readily reduced to butylene glycol.

6. Amino Acid Fermentation : Many bacteria are known to produce amino acids in excess of their requirements. These amino acids include glutamic acid, lysine, tryptophan, threonine and phenylalanine, etc.

Glutamic acid, which is used as monosodium glutamate for flavouring vegetable foods is produced by species of Corynebacterium, Arthobacter, Micrococcus and Brevibacterium. The raw materials used for the production of glutamic acid include a carbon source, such as glucose, molasses, sucrose etc., inorganic salts, a nitrogen source and biotin.

For lysine production, earlier a two step process using two different organisms- E. coli and Aerobacter aerogenes was used. This method is not used any more and has been replaced by the single step process using mutants of Corynebacterium, Brevibacterium, etc. These mutants are grown in a medium containing glucose, an inorganic nitrogen source, and a small concentration of either homoserine, methionine, etc. in addition to a small concentration of biotin.

A strain of E. coli isolated from human faces has been found to produce large amounts of threonine.

7. Retting: In fibre-yielding plants, the fibres which are mostly cellulosic in nature are held together by non-cellulosic materials like pectin or hemicellulose. Retting involves the decomposition of non-cellulosic materials without affecting the fibres.

Fibres of flax, jute, hemp and coconut etc. are obtained by immersing the specific plant organs in stagnant pond water where bacteria develop and cause retting.

8. Production of microbial enzymes: Several enzymes of industrial value are produced by microorganisms. Pectinase and Proteases are products of Clostridium sp. and Bacillus subtilis respectively. The former is used in retting of fibres and the proteases are used as liquid glues, meat tenderizers, beer clarifiers, etc.

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