Process of coagulation of milk proteins occurs due to lactic acid.

Explanation: Lactobacillus bacteria ferment the lactose sugar of milk into lactic acid. The accumulation of lactic acid drops the pH of milk, causing curdling and coagulation of milk casein proteins to produce yoghurt.

Harmful bacteria like Clostridium in the intestine are destroyed due to probiotics.

Explanation: Probiotics contain live beneficial colonies of Lactobacillus and Bifidobacterium that settle in the human intestine. They produce natural antibacterial substances and lower the pH, inhibiting and destroying pathogenic bacteria like Clostridium.

Chemically, vinegar is 4% acetic acid.

Explanation: Ethanol is fermented by Acetobacter and Gluconobacter bacteria to produce acetic acid. A 4% aqueous dilution of this acetic acid is bleached and used as a food preservative and flavoring condiment known as vinegar.

Salts which can be used as supplement of calcium and iron are obtained from gluconic acid.

Explanation: Fermentation of glucose and corn steep liquor by the fungus Aspergillus niger yields gluconic acid. Its mineral salts (calcium gluconate and ferrous gluconate) are widely prescribed as dietary calcium and iron supplements.

A. Microbial Fuels:

1. Methane (Biogas): Produced by anaerobic microbial decomposition of organic urban and agricultural waste.
2. Ethanol (Bio-alcohol): A clean liquid biofuel produced by yeast (Saccharomyces cerevisiae) fermentation of sugarcane molasses.
3. Hydrogen Gas: Produced by photosynthetic bacteria through bio-photolysis of water, considered the cleanest fuel of the future.

B. Why Use Must Increase: Conventional fossil fuels (coal, diesel, petrol) are exhaustible and emit massive quantities of greenhouse gases (CO₂, SO₂). Microbial biofuels are renewable, burn cleanly without toxic residue, and protect our environment from global warming.

1. Marine crude oil spills form a toxic slick on the water surface, suffocating marine life and sea birds.
2. Mechanical skimming is slow and expensive. Biological cleanup (bioremediation) uses specialized bacteria called Hydrocarbonoclastic Bacteria (HCB), such as Pseudomonas spp. and Alcanivorax borkumensis.
3. These bacteria feed on crude oil hydrocarbons and pyridines, enzymatically breaking down toxic compounds into harmless carbon dioxide (CO₂) and water (H₂O).

1. Acid rain contains concentrated sulfuric acid (H₂SO₄) and nitric acid, which increases soil acidity and leaches out essential plant nutrients.
2. Acid-tolerant bacteria like Acidophilum spp. and Acidithiobacillus ferrooxidans utilize sulfuric acid as their source of energy.
3. By metabolizing and neutralizing the acidic sulfur compounds, these bacteria lower soil acidity, restoring normal soil pH and fertility.

1. Chemical pesticides leave toxic synthetic residues (such as fluoroacetamides) that poison groundwater, soil, and human food chains.
2. Bio-pesticides are natural pest-control formulations containing bacterial and fungal toxins (e.g., Bacillus thuringiensis endotoxins, Spinosad, and Trichoderma fungi).
3. They selectively kill targeted insect pests without harming helpful pollinators, earthworms, farm workers, or crop consumers.
4. They biodegrade rapidly and preserve organic soil fertility.

1. Probiotics (yoghurt, kefir, dark chocolate, sauerkraut) contain live colonies of beneficial bacteria like Lactobacillus acidophilus.
2. They improve intestinal microflora, enhance nutrient absorption, and suppress harmful pathogens like Clostridium.
3. They boost the human immune system and relieve digestive disorders like diarrhea and irritable bowel syndrome.
4. When heavy antibiotics wipe out natural gut bacteria, probiotics quickly restore the protective intestinal ecosystem.

1. Baker’s yeast (Saccharomyces cerevisiae) is added to flour dough for fermentation.
2. Yeast ferments dough carbohydrates into ethyl alcohol and CO₂ gas, making the dough rise and giving bread its light, spongy texture.
3. Commercial baker’s yeast is naturally rich in proteins, B-complex vitamins, carbohydrates, and minerals.
4. Fermentation breaks down complex starches into readily digestible nutrients, making yeast-leavened bread highly nutritious.

1. Domestic garbage must be strictly segregated at source into wet biodegradable waste (kitchen scraps, vegetable peels) and dry non-biodegradable waste (plastics, metals, glass).
2. Never mix non-biodegradable items (batteries, medicine wrappers, plastic bags) or hazardous chemical cleaning agents with wet waste, as they kill decomposing bacteria and earthworms.
3. In home compost pits, cover wet organic layers with thin soil or sawdust to maintain aerobic conditions and prevent foul odors and flies.

1. Plastic is non-biodegradable and persists in the environment for hundreds of years.
2. Discarded plastic bags choke storm-water drains and sewer pipelines, causing catastrophic urban waterlogging during monsoons.
3. Stray cattle accidentally swallow plastic bags, which form fatal blockages in their stomachs.
4. Plastic waste entering oceans breaks down into toxic microplastics that poison marine fish and enter human food supplies. Reusable cloth and jute bags must replace plastic bags completely.

1. Wild natural strains of bacteria and fungi produce commercially important compounds (such as antibiotics, vitamins, and enzymes) in very small quantities.
2. By genetic mutations (UV irradiation, chemical mutagens, or recombinant DNA technology), mutant strains are engineered to yield much higher concentrations of desired products in shorter incubation times.
3. Mutant strains tolerate harsh industrial bioreactor conditions (higher temperature, pH variations, and substrate toxicity), making commercial manufacturing far more cost-effective.

1. Microbial enzymes such as proteases, lipases, and amylases effectively break down tough organic stains (blood, sweat, oil, grease, chocolate) into water-soluble molecules.
2. These enzymes operate efficiently at lower water temperatures (30–40°C), saving electric water-heating energy.
3. Adding microbial enzymes makes laundry detergents wash cleaner and faster without fabric degradation.

1. Microbial enzymes are highly specific biocatalysts that operate under mild conditions (low temperature, normal pH, and ambient pressure), saving immense industrial energy.
2. Unlike chemical catalysts, enzymatic reactions do not produce harmful by-products, which eliminates expensive purification and disposal costs.
3. Microbial enzymes are biodegradable, non-toxic, and reusable, making industrial manufacturing green and eco-friendly.

1. In nature, saprophytic bacteria and fungi are the primary biological decomposers.
2. They secrete extracellular digestive enzymes that break down complex organic compounds in plant and animal waste into simple humus.
3. This biological recycling releases essential minerals (nitrogen, phosphorus, potassium) back into the soil, producing nutrient-rich organic compost.

1. Ethanol (C₂H₅OH) is an oxygenated biofuel that improves fuel combustion, significantly reducing emissions of carbon monoxide, unburnt hydrocarbons, and particulate soot.
2. Blending 10% to 20% ethanol into petrol conserves precious foreign exchange spent on importing crude petroleum.
3. Ethanol is renewable, locally produced from sugarcane molasses, and substantially lowers vehicular carbon emissions.

• For Bio-ethanol: Sugarcane, sweet sorghum, maize (corn), sugar beet, and wheat.
• For Bio-diesel: Jatropha curcas, Pongamia pinnata (Karanja), Mahua, rapeseed, soybean, sunflower, and microalgae.

• Solid Biofuels: Firewood, dried crop residues, bagasse, and compressed biomass briquettes.
• Liquid Biofuels: Bio-ethanol, bio-butanol, and bio-diesel.
• Gaseous Biofuels: Biogas (methane + CO₂) and bio-hydrogen gas.