Microorganisms may be invisible to the naked eye, but their roles in human welfare are incredibly vast, diverse, and vital to both environmental balance and industrial processes. Chapter 8 of the NCERT Class 12 Biology textbook, titled “Microbes in Human Welfare,” introduces students to the immense contribution of microbes in sectors like agriculture, food processing, pharmaceuticals, biotechnology, sanitation, and energy. For NEET 2025 aspirants, this chapter is of utmost importance due to its high relevance and weightage in the biology syllabus.

In this chapter, students explore a wide variety of microorganisms, such as bacteria, fungi, protozoa, and viruses, learning how these microscopic organisms are responsible for critical biochemical processes, waste recycling, organic agriculture, and even life-saving medications. Beyond just theory, the practical application of microbial technology in industries and environmental management adds significant value to this topic.

Expanded Key Topics Covered

1. Microbes in Household Products

Certain microbes have been traditionally used in household food preparations for centuries. These include:

  • Curd Production: Lactobacillus species ferment lactose to lactic acid, giving curd its texture and tangy flavor. This also enhances digestibility and improves nutritional value.
  • Baking & Alcohol Production: Saccharomyces cerevisiae (Baker’s yeast) is used for fermentation in baking, as well as the production of ethanol and alcoholic beverages.
  • Fermented Foods: Indian culinary staples like dosa, idli, and bhatura undergo fermentation by natural lactic acid bacteria. The fermentation process improves flavor, texture, and vitamin content.
  • Cheese and Vinegar Production: Specific bacteria and fungi contribute to the aging and flavor of cheese, while Acetobacter aceti is involved in vinegar production.

2. Microbes in Industrial Products

Industrial microbiology uses microbes for large-scale production of valuable compounds:

  • Fermented Beverages: Ethanol is produced on a commercial scale using Saccharomyces cerevisiae under anaerobic conditions.
  • Antibiotics: Discovered by Alexander Fleming, penicillin (from Penicillium notatum) revolutionized medicine. Streptomycin, erythromycin, and tetracycline are other important antibiotics.
  • Organic Acids:
    • Aspergillus niger → Citric acid
    • Acetobacter aceti → Acetic acid
    • Clostridium butylicum → Butyric acid
    • Lactobacillus → Lactic acid
  • Enzymes: Enzymes like proteases and lipases are used in leather, detergent, and paper industries.
  • Bioactive Molecules:
    • Trichoderma polysporum produces cyclosporin A, an immunosuppressive drug used in organ transplant patients.
    • Monascus purpureus produces statins, which help reduce cholesterol levels.

3. Microbes in Sewage Treatment

Wastewater from homes and industries is treated using microbial action before being discharged:

  • Primary Treatment: Physical processes like sedimentation and filtration remove large particles.
  • Secondary (Biological) Treatment: Aerobic bacteria digest organic matter in aeration tanks. The bacterial flocs help reduce BOD (Biological Oxygen Demand).
  • Activated Sludge: The thick floc settles and is transferred to anaerobic sludge digesters where methane-producing bacteria (methanogens) act.
  • Significance: This microbial degradation helps recycle nutrients and reduces environmental pollution.

4. Microbes in Biogas Production

Biogas is a clean, renewable energy source. Its production involves:

  • Methanogens: Methanobacterium breaks down organic waste in the absence of oxygen to release methane.
  • Biogas Plant: A dome-shaped digester is used to process cow dung and organic waste. Methane-rich biogas can be used for cooking and lighting.
  • Benefits: Reduces reliance on fossil fuels, manages waste, and provides nutrient-rich slurry for use as manure.

5. Microbes as Bio-control Agents

Biological control involves using living organisms to control pests and diseases:

  • Trichoderma fungi act as natural fungicides in crop fields.
  • Bacillus thuringiensis (Bt): Produces a protein toxic to insect larvae. Bt toxin is also genetically introduced into crops like Bt cotton to provide pest resistance.
  • Ladybird beetles and dragonflies are other natural biocontrol agents for aphids and mosquitoes, respectively.

6. Microbes as Biofertilizers

These are eco-friendly fertilizers that improve soil quality:

  • Nitrogen-fixing Bacteria:
    • Rhizobium in leguminous plants’ root nodules
    • Azotobacter, Azospirillum are free-living in the rhizosphere
  • Cyanobacteria:
    • Anabaena, Nostoc, and Oscillatoria fix atmospheric nitrogen in rice fields and form symbiotic associations in lichens
  • Mycorrhizae: Symbiotic fungi like Glomus enhance phosphorus uptake

NEET Practice MCQs

  1. Which of the following microbes is used to increase the flavor in cheese?
    • a) Lactobacillus
    • b) Penicillium roqueforti ✅
    • c) Acetobacter
    • d) Streptococcus
  2. Which component is absent in the primary sewage treatment?
    • a) Sedimentation
    • b) Filtration
    • c) Microbial digestion ✅
    • d) Skimming
  3. Which microorganism is used for commercial production of citric acid?
    • a) Aspergillus niger ✅
    • b) Lactobacillus
    • c) Rhizobium
    • d) Monascus purpureus
  4. Bt toxin gene is introduced in plants to provide resistance against:
    • a) Fungal pathogens
    • b) Viral infection
    • c) Insect larvae ✅
    • d) Herbivores
  5. What type of biofertilizer is Nostoc?
    • a) Phosphorus solubilizer
    • b) Nitrogen-fixing cyanobacterium ✅
    • c) Mycorrhiza
    • d) Sulphur oxidizer

Frequently Asked Questions (FAQs)

Q1. How does fermentation by microbes improve food quality?
 Fermentation enhances flavor, increases nutritional value, preserves food, and makes it easier to digest.

Q2. What is the significance of microbial flocs in wastewater treatment?
 Flocs are aggregates of bacteria and fungal filaments that digest organic matter, thereby reducing BOD and purifying water.

Q3. Can microbes reduce environmental pollution?
 Yes, through waste degradation, sewage treatment, and replacing chemical fertilizers and pesticides with biofertilizers and biopesticides.

Q4. How are antibiotics discovered?
 Most antibiotics are produced by fungi or actinomycetes. They are discovered by observing microbial interactions where one microbe inhibits the growth of another.

Q5. Are biofertilizers better than chemical fertilizers?
 Yes. They are eco-friendly, cost-effective, sustainable, and do not lead to soil degradation like chemical fertilizers.

NEET Preparation Tips for Chapter 8

  • Create a table summarizing microbes, their uses, and their industrial products.
  • Use visual aids like flowcharts for sewage treatment steps.
  • Practice assertion-reason type questions for conceptual clarity.
  • Revise microbial examples with their scientific names and spellings.
  • Solve at least 20 PYQs from this chapter to strengthen retention.

Conclusion

Chapter 8, “Microbes in Human Welfare,” provides invaluable insights into the beneficial uses of microorganisms in modern society. These tiny organisms play a giant role in improving human life — from energy production and waste management to agriculture and pharmaceuticals. Understanding this chapter not only sharpens NEET readiness but also builds appreciation for sustainable science and green technology. By mastering the examples and underlying principles, students can confidently tackle high-weightage NEET questions and foster a scientific mindset rooted in real-world application.