Microbes in Human Welfare: Class 12 NCERT Biology Explained

Role of Microbes in Food Production

Microbes are vital in producing many traditional and modern foods consumed in India. Lactic acid bacteria found in curd, yogurt, and pickles ferment milk and vegetables, enhancing taste and shelf life. Yeast, a fungus, ferments sugars in dough to produce carbon dioxide, making bread soft and fluffy.

Traditional Indian foods like idli, dosa, and dhokla rely on microbial fermentation of rice, urad dal, and Bengal gram batter. This process improves digestibility and nutritional value.

Examples of microbial roles in food:

• Lactic acid bacteria produce curd and fermented vegetables.
• Yeast helps in bread and alcoholic beverages.
• Moulds like Aspergillus oryzae ferment soybeans for soy sauce.

Microbial fermentation also produces gases such as carbon dioxide and methane, which are by-products of metabolism. This natural process is eco-friendly and enhances food quality.

Microbes as Biocontrol Agents in Agriculture

Biocontrol uses living organisms to manage pests and diseases, offering an eco-friendly alternative to harmful chemical pesticides. Chemical pesticides can cause pollution and health risks.

Natural predators like ladybird beetles consume aphids, and dragonflies eat mosquitoes, maintaining ecological balance. Microbes such as Bacillus thuringiensis (Bt) produce toxins lethal to specific insect pests without harming other organisms. Bt spores sprayed on crops kill caterpillars feeding on plants.

Genetic engineering has introduced Bt toxin genes into cotton plants, producing Bt-cotton that resists insect attacks, reducing pesticide use.

Fungi like Trichoderma species colonize plant roots and inhibit harmful pathogens, while baculoviruses specifically infect insect pests, acting as biological insecticides.

This approach supports sustainable agriculture and protects biodiversity.

Microbes as Biofertilizers Enhancing Soil Fertility

Biofertilizers are microbial inoculants that enrich soil nutrient content by fixing atmospheric nitrogen or solubilizing phosphorus. They reduce the need for chemical fertilizers, promoting sustainable farming.

Common biofertilizers include:

• Rhizobium bacteria, which form nodules on legume roots and fix nitrogen.
• Azotobacter and Azospirillum, free-living nitrogen-fixing bacteria.
• Blue-green algae (cyanobacteria) that fix nitrogen in paddy fields.
• Phosphate-solubilizing bacteria that make phosphorus available to plants.

Using biofertilizers improves soil health, increases crop yield, and reduces environmental pollution. Farmers practicing organic agriculture rely heavily on these microbes.

Worked example: If 1 hectare of legume crop is inoculated with Rhizobium, it can fix approximately 100 kg of nitrogen per crop cycle, reducing synthetic fertilizer use and cost.

Industrial Applications of Microbes

Microbes are indispensable in various industries due to their ability to produce valuable products through fermentation and biochemical processes.

Key industrial applications include:

• Antibiotics production: Penicillium mould produces penicillin.
• Enzymes: Microbial enzymes like amylase and protease are used in detergents and food processing.
• Alcoholic beverages: Yeast ferments sugars to produce alcohol in beer and wine.
• Organic acids: Lactic acid bacteria produce lactic acid used in food and pharmaceuticals.
• Vitamins and amino acids: Microbes synthesize vitamins like B12 and amino acids for supplements.

Microbial fermentation is a cost-effective, scalable, and eco-friendly method, making microbes central to biotechnology industries.

Formula: Fermentation reaction by yeast:

$$\text{C}_6\text{H}_{12}\text{O}_6 \rightarrow 2 \text{C}_2\text{H}_5\text{OH} + 2 \text{CO}_2$$

(Glucose → Ethanol + Carbon dioxide)

Environmental Benefits of Microbes in Human Welfare

Microbes contribute significantly to environmental sustainability by decomposing organic waste and treating sewage. They help recycle nutrients, maintaining ecosystem balance.

In bioremediation, microbes degrade pollutants like oil spills and pesticides, cleaning contaminated environments naturally.

Methanogenic bacteria break down organic matter anaerobically in biogas plants, producing methane used as renewable energy.

Using microbial processes reduces chemical waste and pollution, aligning with eco-friendly practices promoted in modern agriculture and industry.