Learning Objectives
- Understand the role of microbes in household products and industries
- Learn about microbes in sewage treatment
- Study biogas production and biocontrol agents
- Understand microbes as biofertilizers
Key Concepts
Microbes in Household Products
Lactobacillus: Converts milk to curd (lactic acid production). Baker's yeast (Saccharomyces cerevisiae): Used in bread making (CO2 causes dough to rise) and brewing. Toddy: Traditional drink from fermented palm sap. Cheese: Large holes in Swiss cheese due to CO2 from Propionibacterium shermanii. Roquefort cheese ripened by Penicillium roqueforti. Fermented foods: Idli, dosa (fermentation by bacteria and yeast).
Microbes in Industrial Products
Antibiotics: Penicillium notatum → Penicillin (discovered by Alexander Fleming, 1928). Full scale production by Ernst Chain and Howard Florey. Organic acids: Citric acid (Aspergillus niger), Acetic acid (Acetobacter aceti), Butyric acid (Clostridium butylicum), Lactic acid (Lactobacillus). Alcoholic beverages: Beer, wine, whisky — fermentation by yeast. Wine → distillation → brandy. Enzymes: Lipases (detergents), Pectinases and Proteases (fruit juice clarification), Streptokinase (clot buster, from Streptococcus). Statins: From Monascus purpureus (yeast) — lower cholesterol by inhibiting HMG-CoA reductase. Cyclosporin A: From Trichoderma polysporum — immunosuppressant in organ transplants.
Microbes in Sewage Treatment
Primary treatment: Physical — sedimentation, filtration to remove large particles and grit. Secondary (Biological) treatment: Aerobic microbes in aeration tanks digest organic matter in sewage → reduce BOD (Biochemical Oxygen Demand). BOD: Amount of O2 consumed by microbes to decompose organic matter — high BOD = more polluted water. Effluent passes to settling tank → anaerobic sludge digester → biogas (CH4, CO2, H2S) produced. Treated water released.
Biogas Production
Produced by methanogenic bacteria (methanogens, e.g., Methanobacterium) under anaerobic conditions. Cattle dung (gobar) is main substrate in Indian biogas plants. Biogas composition: mainly CH4 (methane) + CO2 + H2S. Technology developed by IARI (Indian Agricultural Research Institute) and KVIC (Khadi and Village Industries Commission).
Biocontrol Agents
Using biological organisms to control pests instead of chemicals. Bacillus thuringiensis (Bt) — produces Cry proteins (crystal proteins) toxic to insect larvae. Used as biopesticide. Trichoderma — biocontrol of plant diseases. Nucleopolyhedrovirus (NPV) — baculoviruses that kill insects (species-specific, eco-friendly). Ladybird beetles and dragonflies — biocontrol of aphids and mosquitoes respectively.
Biofertilizers
Living organisms that enrich soil nutrients. Nitrogen fixers: Rhizobium (symbiotic, in legume root nodules), Azospirillum and Azotobacter (free-living). Cyanobacteria: Nostoc, Anabaena — fix nitrogen, add organic matter. Important in paddy fields. Mycorrhiza: Symbiotic fungi (e.g., Glomus) associated with plant roots. Absorb phosphorus from soil and transfer to plant. Also increase drought resistance.
Summary
Microbes play vital roles in food production, industrial products, sewage treatment, biogas production, biocontrol, and biofertilization. Antibiotics, organic acids, and enzymes are major industrial products. Sewage treatment uses aerobic and anaerobic microbes. Biocontrol agents like Bt and Trichoderma offer eco-friendly pest management. Biofertilizers enhance soil fertility naturally.
Important Terms
- BOD: Biochemical Oxygen Demand — measure of organic pollution in water
- Methanogens: Anaerobic archaea that produce methane during decomposition
- Cry proteins: Crystal proteins from Bt bacteria toxic to specific insect larvae
- Mycorrhiza: Symbiotic association of fungi with plant roots for nutrient absorption
- Statin: Cholesterol-lowering agent from Monascus yeast
- Cyclosporin A: Immunosuppressive drug from Trichoderma
- Penicillin: First antibiotic discovered by Fleming from Penicillium
- Biofertilizer: Living organism that enriches soil nutrient quality
Quick Revision
- Curd: Lactobacillus; Bread: yeast; Swiss cheese: Propionibacterium
- Penicillin: Fleming (discovered); Chain & Florey (mass production)
- Statin: Monascus purpureus; Cyclosporin A: Trichoderma polysporum
- Sewage: primary (physical) → secondary (biological, reduce BOD) → anaerobic digestion
- Biogas: methanogens, anaerobic, cattle dung substrate
- Bt: Bacillus thuringiensis → Cry proteins → insecticidal
- Rhizobium (legumes), Azotobacter (free-living) — nitrogen fixers
- Mycorrhiza (Glomus): phosphorus absorption from soil