Microorganisms are very tiny living things. Microorganisms are classified into four major groups. These groups are bacteria, fungi, protozoa and some algae. Microorganisms are used for various purposes.
1. Microbes in sewage treatment
• The municipal waste-water known as sewage contains large amounts of organic matter and microbes. These microorganisms are used for treatment of waste water.
• In the primary stage of waste water treatment physical removal of particles from the sewage through filtration and sedimentation occurs.
• In the secondary stage of waste water treatment the primary effluent is passed into large aeration tanks, this allows vigorous growth of aerobic microbes into flocs.
These microbes consume the major part of the organic matter in the effluent. This significantly reduces the BOD (biochemical oxygen demand) of the effluent. BOD is a measure of the organic matter present in the water. The greater the BOD of waste water, more is its polluting potential.
• Further in the anaerobic sludge digesters bacteria produce a mixture of gases such as methane, hydrogen sulphide and carbon dioxide. These gases form biogas.
2. Microbes in production of biogas
• Certain bacteria, which grow anaerobically on cellulosic material, produce large amount of methane along with CO2 and H2
• These bacteria are collectively called methanogens, and one such common bacterium is Methanobacterium. These bacteria are commonly found in the anaerobic sludge during sewage treatment and produces biogas.
*Methogens are also present in the rumen (a part of stomach) of cattle. A lot of cellulosic material present in the food of cattle is also present in the rumen. In rumen, these bacteria help in the breakdown of cellulose and play an important role in the nutrition of cattle.*
• The technology of biogas production was developed in India mainly due to the efforts of Indian Agricultural Research Institute (IARI) and Khadi and Village Industries Commission (KVIC).
3. Microbes as biocontrol agents
• Biocontrol refers to the use of biological methods for controlling plant diseases and pests.
• In agriculture for controlling pests natural predation methods should be used rather than use of chemicals.
• An important part of the biological farming approach is to become familiar with the various life forms that inhabit the field, predators as well as pests, and also their life cycles, patterns of feeding and the habitats that they prefer. This will help develop appropriate means of biocontrol.
• Some examples:
– Lady bird – to control aphids
– Dragon fly – to control mosquitoes
– Bacillus thuringiensis (Bt Cotton) – to control wide range insects
– Trichoderma (fungi) – protects root system and control plant pathogens.
– Baculoviruses (Nucleopolyhedrovirus) – to attack insects and other arthropods.
• This is especially desirable when beneficial insects are being conserved to aid in an overall integrated pest management (IPM) programme, or when an ecologically sensitive area is being treated.
4. Microbes as biofertilisers
• Biofertilisers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilisers are bacteria, fungi and cyanobacteria.
Bacteria: Symbiosis – Rhizobium with root nodules of leguminous plants; Free living (in the soil) – Azotobacter and Azospirillum.
Fungi: Symbiosis – Mycorrhiza with root system of genus Glomus and absorb phosphorus and water from the soil for the plant growth.
Cyanobacteria: Symbiosis – Anabaena in Azolla; Free living – Nostoc, Oscillatoria and Blue green algae.
5. Production of alcohol and wine
Microorganism such as Yeast is used for the large scale production of alcohol, wine and acetic acid (vinegar).
6. Production of antibiotics
• Antibiotics are chemical substances, which are produced by some microbes and can kill or retard the growth of other (disease-causing) microbes such as Penicillin.
• Antibiotics are even mixed with the feed of livestock and poultry to check microbial infection in animals. They are also used to control many plant diseases.
7. Production of Amino acids
• It is used for production of amino acids on a commercial scale. They are used in food industry as flavor and taste enhances (Eg: Glutamic acid), as artificial sweeteners in soft drink industry (Eg: Glycine, Aspartame), in pharmaceutical industry (Eg: Ornithine- treatment of liver disease, Histidine and Glutamine- therapy for ulcers).
8. Production of Chemicals, Enzymes and other Bioactive Molecules
• Microbes are being used for commercial and industrial production of certain chemicals like organic acids, alcohols, enzymes and other bioactive molecules.
• The organic acids produced industrially along with the microbes used are listed in the table given below:
• The list of enzymes produced by microbes and their uses are given in the table below: