Unit 3: Biology and Human Welfare

Chapter 2: Microbes in Human Welfare

Microbes in Household Products

• Curd: Lactobacillus (Lactic Acid Bacteria) ferments milk.
• Bread: Saccharomyces cerevisiae (Yeast) causes dough to rise.
• Cheese: Bacteria and fungi are used for ripening and flavor (e.g., Swiss cheese, Roquefort cheese).
• Dosa & Idli: Fermentation by bacteria.

Microbes in Industrial Products

• Fermented Beverages: Yeast (Saccharomyces) produces ethanol (wine, beer).
• Antibiotics: Penicillin from Penicillium notatum.
• Organic Acids: Citric acid (Aspergillus niger), Acetic acid (Acetobacter aceti).
• Enzymes: Lipases (detergents), Pectinases (juice clarification), Streptokinase (clot buster).
• Bioactive Molecules: Cyclosporin A (immunosuppressant), Statins (cholesterol-lowering).

Microbes in Sewage Treatment

• Primary Treatment: Physical removal of solids.
• Secondary Treatment (Biological):
  • Aerobic microbes in aeration tanks consume organic matter, reducing BOD (Biochemical Oxygen Demand).
  • Anaerobic bacteria in sludge digesters produce biogas.

Microbes in Biogas Production

• Biogas: Mixture of methane, CO2, and H2S.
• Methanogens: Anaerobic bacteria (e.g., Methanobacterium) that produce methane.
• Process: Anaerobic digestion of organic waste (e.g., cow dung) in a biogas plant.

Microbes as Biocontrol Agents

• Using biological methods to control pests and diseases.
• Examples:
  • Bacillus thuringiensis (Bt): Kills insect larvae (e.g., caterpillars).
  • Trichoderma (fungus): Controls plant pathogens.
  • Nucleopolyhedrovirus (NPV): Species-specific insect viruses.

Microbes as Biofertilizers

• Organisms that enrich soil nutrient quality.
• Examples:
  • Nitrogen-fixing Bacteria:
    • Rhizobium (symbiotic in legumes)
    • Azotobacter (free-living)
  • Cyanobacteria (Blue-green algae): Anabaena, Nostoc.
  • Mycorrhiza: Symbiotic fungi that help in phosphorus uptake.