Microbes in Human Welfare – Class 12 Biology Notes | Full NCERT Chapter Summary

 🦠 Chapter 10: Microbes in Human Welfare



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🔹 Introduction


Microbes = Bacteria, fungi, protozoa, algae, viruses.


Helpful in:


Food industry


Medicine


Agriculture


Sewage treatment


Biogas production





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🔹 Microbes in Household Products


Lactobacillus – used to curdle milk


Yeast (Saccharomyces cerevisiae) – used in bread and alcoholic beverages


Fermented foods – dosa, idli, toddy



📌 Diagram: Fermentation process in food preparation



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🔹 Microbes in Industrial Products


Product Microbe


Ethanol Saccharomyces cerevisiae

Citric acid Aspergillus niger

Acetic acid Acetobacter aceti

Antibiotic (Penicillin) Penicillium notatum



📌 Diagram: Fermenter setup in industry



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🔹 Microbes in Antibiotics


Antibiotic = Substance produced by microbe that kills other microbes


First antibiotic: Penicillin, discovered by Alexander Fleming (1928)




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🔹 Microbes in Chemicals, Enzymes and Bioactive Molecules


Streptokinase (clot buster) – Streptococcus


Cyclosporin A (immunosuppressant) – Trichoderma polysporum


Statins (cholesterol-lowering) – Monascus purpureus




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🔹 Microbes in Sewage Treatment


Treatment stages:


1. Primary treatment (physical)



2. Secondary treatment (biological)


Use of aerobic bacteria in aeration tank


BOD (Biochemical Oxygen Demand) reduced




3. Sludge → anaerobic digestion → biogas





📌 Diagram: Sewage treatment plant



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🔹 Microbes in Biogas Production


Methanogens (e.g., Methanobacterium)


Produce methane, CO₂, H₂


Use: Rural cooking fuel



📌 Diagram: Biogas plant structure



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🔹 Microbes as Biocontrol Agents


Control pests using natural predators/pathogens


Example:


Trichoderma – fungus against plant pathogens


Bacillus thuringiensis (Bt) – used in Bt-cotton





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🔹 Microbes as Biofertilisers


Improve soil fertility naturally


Example:


Rhizobium – N₂-fixation in legumes


Azospirillum, Azotobacter – free-living N₂-fixers


Cyanobacteria – e.g., Anabaena, Nostoc




📌 Diagram: Nitrogen fixation process



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🖼️ Important Diagrams to Include:


1. Fermenter for industrial product



2. Biogas plant



3. Sewage treatment plant



4. Nitrogen cycle / Biofertiliser chart




5. Bt cotton mode of action



6. Penicillin discovery (illustrative chart)





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✍️ Written by: Shahid – Study with Shahid

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