Microbes in Human Welfare Class 12 Notes | NCERT Chapter 8 PDF. + PYQ NEET

Hello friend,

I am NEET Dropper. Today I'm sharing complete notes *Chapter 8: Microbes in Human Welfare* 🦠

NCERT / FULL SHORT NOTES

CBSE New NCERT 2027

### *1. MICROBES IN HOUSEHOLD PRODUCTS* 🏠

**Product** **Microbe** **Imp Point**

**Curd/Dahi** *Lactobacillus* = LAB Milk → Lactic acid → Coagulation. Vit B12 ↑. Checks pathogens

**Idli/Dosa** Bacteria CO2 → Puffed dough

**Bread** *Saccharomyces cerevisiae* Yeast fermentation → CO2 → Dough rises

**Toddy** Yeast Fermented sap of palm

**Cheese** Fungi + Bacteria **Swiss cheese**: *Propionibacterium sharmanii* → CO2 → Large holes

**Roquefort cheese**: *Penicillium roqueforti*

*Diagram: LAB growing in milk*

Milk + Lactobacillus → 30-40°C → Lactic acid formation → Casein coagulation → Curd

---

### *2. MICROBES IN INDUSTRIAL PRODUCTS* 🏭

*Fermentors* = Large vessels for industrial production

**Category** **Product** **Microbe** **NEET Point**

**Beverages** Wine, Beer *S. cerevisiae* Ethanol without distillation

**Antibiotics** **Penicillin** *Penicillium notatum* 1st antibiotic, A. Fleming

**Organic Acid** **Citric acid** *Aspergillus niger*

**Acetic acid** *Acetobacter aceti*

**Butyric acid** *Clostridium butylicum*

**Enzymes** **Streptokinase** *Streptococcus* Clot buster, removes clots

**Lipase** Fungi Used in detergents

**Bioactive** **Cyclosporin A** *Trichoderma polysporum* Immunosuppressant in organ transplant

**Statins** *Monascus purpureus* Blood cholesterol ↓

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### *3. MICROBES IN SEWAGE TREATMENT* 🚰

*Sewage* = Waste water with human excreta. *STP* = Sewage Treatment Plant

*Diagram: Sewage Treatment Plant*

Sewage → Primary Treatment

↓ Filtration + Sedimentation

Primary Sludge + Effluent

↓

Secondary Treatment → Aeration Tank + Flocs

↓ BOD reduced drastically

Settling Tank → Activated Sludge + Clean Effluent → River

↓

Anaerobic Sludge Digester → Biogas: CH4 + CO2 + H2S

*Imp Terms*:

1. *Flocs* = Masses of bacteria + fungal filaments in aeration tank

2. *BOD* = Biological Oxygen Demand = O2 required by microbes to decompose organic matter

*↑ BOD = ↑ Water pollution* 🔥Most Imp for NEET

3. *Activated sludge* = Small part reused as inoculum, major part → Anaerobic digester

4. *Methanogens* = _Methanobacterium_ → Biogas produce karte hain

*Ganga Action Plan + Yamuna Action Plan* = Ministry of Environment & Forests

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### *4. MICROBES IN BIOGAS PRODUCTION* 🔥

*Biogas Composition*: 50-70% CH4 + 30-40% CO2 + H2 + H2S

*Microbe*: _Methanobacterium_ = Methanogen

*Diagram: Biogas Plant*

Gas Holder (Floating Cover)

↑

Concrete Tank ← Dung + Water Slurry Inlet

↓

Digester Chamber → Anaerobic digestion by methanogens

↓

Outlet → Spent slurry = Fertilizer

*IARI + KVIC* = Technology developed

*Benefit*: Cooking fuel + Fertilizer + No smoke

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### *5. MICROBES AS BIOCONTROL AGENTS* 🐞

*Biocontrol* = Use of life forms to control pests, not chemicals

**Agent** **Used Against** **Special Point**

**Ladybird** Aphids

**Dragonflies** Mosquitoes

**Bacillus thuringiensis = Bt** Butterfly caterpillars **Bt toxin** gene → **Bt cotton**. Available in sachets

**Trichoderma** Soil-borne plant pathogens Free-living fungus, root ecosystem

**Baculovirus** Insects, Arthropods *Nucleopolyhedrovirus*. **Narrow spectrum**, species specific. No harm to non-target organisms

*IPM* = Integrated Pest Management

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### *6. MICROBES AS BIOFERTILIZERS* 🌱

*Biofertilizer* = Organisms that enrich nutrient quality of soil

**Type** **Example** **Function**

**Symbiotic N2 fixer** *Rhizobium* in legume root nodules N2 → Organic nitrogen

**Free-living N2 fixer** *Azotobacter*, *Azospirillum* N2 fixation in soil

**Cyanobacteria** *Anabaena*, *Nostoc*, *Oscillatoria* N2 fixation. **Imp for paddy fields**

**Mycorrhiza** *Glomus* = Fungi **Phosphorus absorption** ↑. Tolerance to drought, salinity, root pathogens

*Benefit*: Chemical fertilizers ↓ → Soil pollution ↓

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### *NEET/BOARD PYQ HOTSPOTS* 💯

1. *BOD full form + meaning* - 10+ times

2. *Methanogen* = _Methanobacterium_, found in rumen of cattle + biogas

3. *Swiss cheese holes* = _Propionibacterium sharmanii_ due to CO2

4. *Statins source* = _Monascus purpureus_ → Cholesterol lowering

5. *Cyclosporin A* = _Trichoderma_ → Immunosuppressant

6. *Bt toxin* = _Bacillus thuringiensis_ → Insect resistant plants

7. *Mycorrhiza* = _Glomus_ → Phosphorus absorption

8. *Streptokinase* = _Streptococcus_ → Clot buster

9. *Penicillin discoverer* = Alexander Fleming

10. *Baculovirus* = Narrow spectrum, no harm to mammals/birds

*1-Page Yaad Karne Ka Trick*:

*Doodh* = LAB, Swiss-CO2 | *Factory* = Citric-_Aspergillus_, Statins-_Monascus_

*Ganda Paani* = BOD, Flocs, Methanogen | *Kheti* = Bt-cotton, _Glomus_-P, _Rhizobium_-N2