Biology · ZoologyZOO 10
Microbes in Human Welfare
Biogas, sewage treatment, antibiotics, biofertilisers, biocontrol — beneficial microorganisms
Concept Core
Essential theory — everything NCERT tests on Microbes in Human Welfare
MICROBES IN FOOD & INDUSTRY
Lactobacillus: curd production (lactic acid). Saccharomyces cerevisiae: bread (CO₂ leavening), beer/wine (fermentation). Propionibacterium shermanii: Swiss cheese holes (CO₂) + taste. Aspergillus niger: citric acid. Acetobacter aceti: acetic acid (vinegar).
ANTIBIOTICS & ENZYMES
Penicillin: from Penicillium notatum (Fleming, 1928). First antibiotic. Inhibits bacterial cell wall synthesis.
Streptomycin: from Streptomyces griseus. Tetracycline, erythromycin: from Streptomyces sp.
Industrial enzymes: Lipases (detergent), Proteases (cheese), Streptokinase (clot buster from Streptococcus), Cyclosporin A (immunosuppressant from Trichoderma).
SEWAGE TREATMENT
Primary treatment: physical removal of large solids (filtration, sedimentation). Secondary (biological): BOD reduction using microorganisms. Flocs (microbe+organic matter clumps) → settled as sludge. Effluent: reduced BOD.
Anaerobic sludge digestion: bacteria produce biogas (CH₄ + CO₂ + H₂S) from sludge. Biogas used as fuel.
BIOGAS & BIOCONTROL
Biogas: mainly methane (CH₄). Gobar gas plants use cow dung (methanogen bacteria). IARI & KVIC (Khadi Village Industries Commission) promote biogas in India.
Biocontrol: Bacillus thuringiensis (Bt) toxin kills insects (used in Bt cotton). Nucleopolyhedrovirus (baculovirus) — safe for non-target organisms. Trichoderma: fungal biocontrol agent. Ladybird, dragonfly: insect predators.
BIOFERTILISERS
Rhizobium: symbiotic N₂ fixation (legumes). Azospirillum, Azotobacter: free-living N₂ fixers. Cyanobacteria (Anabaena, Nostoc): fix N₂ in rice paddies. Mycorrhiza: fungal symbiosis with roots — phosphorus absorption. PSB (Phosphate Solubilising Bacteria).
Fact & Formula Vault
High-yield facts, numbers, and formulas
Microbe → Product
Lactobacillus → curd (lactic acid)
Saccharomyces → bread, beer, wine
Propionibacterium → Swiss cheese
Penicillium → Penicillin (antibiotic)
Aspergillus niger → citric acid
Sewage Treatment
Primary: physical (filtration)
Secondary: biological (BOD reduction)
Flocs: microbe+organic clumps
Biogas from sludge: CH₄, CO₂, H₂S
Biofertilisers
Rhizobium: legume symbiont
Azotobacter: free-living aerobe
Anabaena/Nostoc: rice paddies
Mycorrhiza: phosphorus uptake
PSB: phosphate solubilisation
Worked Examples
NEET-style questions solved step-by-step
EASYPenicillin was discovered by:▾
Penicillin was discovered by:
Alexander Fleming in 1928 from Penicillium notatum. He observed that Staphylococcus colonies near Penicillium mould were lysed. First antibiotic used clinically.
MEDIUMBOD (Biological Oxygen Demand) is a measure of:▾
BOD (Biological Oxygen Demand) is a measure of:
Organic matter pollution in water. Higher BOD = more organic matter = more microbial activity needed = less O₂ available. Secondary sewage treatment reduces BOD by allowing microbes to decompose organic matter.
HARDStreptokinase (clot buster) is produced by:▾
Streptokinase (clot buster) is produced by:
Streptococcus bacteria. It dissolves blood clots (thrombolytic therapy). It is a recombinant version now used in heart attack treatment. NOT from Streptomyces (different genus).
Mistake DNA
Common NEET traps for this chapter
⚠ Penicillium vs Streptomyces antibiotics
Penicillin = from Penicillium (fungus). Streptomycin, tetracycline = from Streptomyces (bacteria). Common confusion.
✓ Fix: Penicillin = Penicillium (P matches P). Streptomycin = Streptomyces.
⚠ Biogas vs Biofuels
Biogas = mainly CH₄ from anaerobic digestion of organic matter. NOT the same as biodiesel or bioethanol.
✓ Fix: Biogas = CH₄ (methane). Produced by methanogens anaerobically.
⚠ Bt toxin source
Bt toxin is from Bacillus thuringiensis (bacterium), NOT from a fungus. The toxin gene is now also inserted into Bt cotton (transgenic plant).
✓ Fix: Bt = Bacillus thuringiensis. Toxin is a protein that kills insect larvae.
Chapter Intelligence
Exam data and last-minute strategy
NEET Frequency
1–2 Q/year. Penicillin discovery, BOD/sewage treatment, biogas composition, biofertiliser organisms, Bt toxin source.
High-Yield
Fleming + Penicillium = Penicillin. BOD = organic pollution measure. Biogas = CH₄. Rhizobium = legume symbiont. Bt = Bacillus thuringiensis. Streptokinase = Streptococcus.
Strategy
Make a microbe → product table (10 rows). Know sewage treatment steps in order. These cover nearly all NEET questions on this chapter.
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