Ch 10 covers the beneficial roles of microbes — in household products (curd, bread, fermented foods), industry (antibiotics, chemicals, enzymes), sewage treatment, biogas production, biocontrol, and biofertilisers.
Household: Lactobacillus (curd), yeast (bread, idli, dosa), Propionibacterium (Swiss cheese). Industrial: Aspergillus (citric acid), Clostridium (butyric acid), Saccharomyces (ethanol). Antibiotics: Penicillium notatum (penicillin). Enzymes: lipases, proteases, streptokinase (clot buster). Bioactive molecules: cyclosporin A (immunosuppressant), statins (cholesterol-lowering).
Sewage treatment: primary (physical — settling), secondary (biological — aerobic bacteria in activated sludge, BOD reduction), effluent release. Biogas: anaerobic digestion (methanogens) in gobar gas plants. Biocontrol: Bt (Bacillus thuringiensis — insecticidal protein), Trichoderma (fungal pathogen control), ladybugs (aphid control). Biofertilisers: Rhizobium (N₂ fixation in legumes), blue-green algae, Azolla, mycorrhiza (phosphorus uptake).
Download: https://ncert.nic.in/textbook/pdf/lebo110.pdf | Complete book: https://ncert.nic.in/textbook/pdf/lebo1ps.zip
BOD (Biochemical Oxygen Demand) is the amount of dissolved oxygen consumed by microorganisms to decompose organic matter in water. High BOD indicates heavy organic pollution. In secondary sewage treatment, aerobic bacteria reduce BOD by consuming organic matter. Treated water should have low BOD before discharge into natural water bodies, ensuring aquatic life is not harmed by oxygen depletion.
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