Botany Microbes in Human Welfare - Class 12 JKBOSE Botany

Microbes in Human Welfare

Microbes are microscopic organisms not visible to the naked eye, requiring a microscope for observation. They include bacteria, fungi, viruses, protozoa, viroids, and prions. While often associated with diseases and food spoilage, many microbes are highly beneficial to humans in various sectors such as food production, industry, environmental management, and agriculture.

Types of Microbes and Their General Roles

Microbes encompass a diverse group of organisms with both harmful and beneficial effects. They are agents of infectious diseases in humans, animals, and plants, and can spoil food items. However, several microbes are essential for producing…

Microbes in Human Welfare

Microbes are microscopic organisms not visible to the naked eye, requiring a microscope for observation. They include bacteria, fungi, viruses, protozoa, viroids, and prions. While often associated with diseases and food spoilage, many microbes are highly beneficial to humans in various sectors such as food production, industry, environmental management, and agriculture.

Types of Microbes and Their General Roles

Microbes encompass a diverse group of organisms with both harmful and beneficial effects. They are agents of infectious diseases in humans, animals, and plants, and can spoil food items. However, several microbes are essential for producing food products, industrial chemicals, antibiotics, and environmental management.

• Types of microbes: Bacteria, fungi, yeast, viruses, prions, protozoa.
• Harmful roles: Cause diseases, spoil food.
• Beneficial roles: Used in food production, industry, sewage treatment, biogas production, biocontrol, and as biofertilizers.

Microbes in Household Products

Microbes play a crucial role in the preparation of various household food products such as curd, fermented foods, and cheese. Their metabolic activities transform raw ingredients into consumable products with improved nutritional and sensory qualities.

• Curd formation: Involves adding a small amount of curd (inoculum) containing Lactobacillus acidophilus to milk. The bacteria convert lactose (milk sugar) into lactic acid, which partially digests casein protein, leading to coagulation and curd formation.
• Nutritional benefits: Curd contains vitamin B12, strengthens the immune system, and maintains healthy nerve cells. Lactic acid bacteria suppress harmful bacteria in the stomach.
• Fermented products: Yeast (Saccharomyces cerevisiae) is used for alcoholic fermentation, producing ethanol and CO₂. CO₂ causes the dough to rise, giving bread its soft, porous texture.
• Bread: Dough is fermented by Saccharomyces cerevisiae (baker’s yeast), producing CO₂.
• Toddy: A traditional South Indian alcoholic beverage produced by fermenting palm sap with naturally occurring yeast (Saccharomyces cerevisiae), containing about 6% ethanol.
• Cheese: Made from milk by acidification and separation of water and fat. Final ripening uses specific microbes:
  • Swiss cheese: Large holes due to Propionibacterium shermanii.
  • Roquefort cheese: Small holes due to the fungus Penicillium roqueforti.

Microbes in Industrial Products

Microbes are used on an industrial scale to synthesize products such as alcoholic beverages, antibiotics, organic acids, enzymes, and bioactive molecules. Large fermenters are employed for mass production.

• Alcoholic beverages: Industrial fermentation of sugars by yeast (Saccharomyces cerevisiae) in large fermenters produces ethanol and CO₂.
• Types of drinks and raw materials:
  • Beer: Barley (Hordeum vulgare), undistilled.
  • Wine: Grapes, undistilled.
  • Rum: Sugarcane, distilled.
  • Whisky: Produced by distilling beer.
  • Brandy: Produced by distilling wine.
• Alcohol concentration: Undistilled drinks (beer, wine) have lower ethanol content; distilled drinks (whisky, brandy, rum) have higher ethanol content.

Antibiotics

Antibiotics are chemical substances produced by certain microbes (bacteria and fungi) that kill or inhibit the growth of disease-causing microorganisms. They are crucial in treating bacterial infections.

• Definition: “Anti” means against, “bios” means life; antibiotics act against the life of disease-causing microbes but are beneficial to humans.
• Discovery: The first antibiotic, penicillin, was discovered accidentally by Alexander Fleming while working with Staphylococcus bacteria. A mold (Penicillium notatum) inhibited bacterial growth, leading to the identification of penicillin.
• Development: Ernest Chain and Howard Florey, along with Fleming, developed penicillin for medical use. All three received the Nobel Prize in 1945.
• Historical significance: Penicillin was extensively used to treat wounded American soldiers during World War II.

Industrial Production of Organic Acids, Enzymes, and Bioactive Molecules

Microbes are sources of various organic acids, enzymes, and bioactive molecules used in food, industry, and medicine. The following table summarizes key products, their microbial sources, and uses:

Microbes in Sewage Treatment

Microbes are essential in treating municipal sewage to reduce pollution before discharge into water bodies. Sewage contains dissolved and undissolved organic waste, including human excreta and food residues.

• Sewage treatment steps:
  1. Physical (Primary) Treatment: Involves filtration (removal of floating debris) and sedimentation (settling of sand, soil, pebbles). Results in primary effluent (liquid) and primary sludge (solid).
  2. Biological (Secondary) Treatment: Primary effluent is transferred to an aeration tank (Tank 1), where aerobic bacteria digest dissolved organic waste, forming bacterial flocs (aggregates of bacteria and fungi). Continuous agitation and oxygen supply are maintained.
  3. BOD (Biochemical Oxygen Demand): Indicates the amount of oxygen required by aerobic bacteria to decompose organic matter in 1 liter of wastewater. High BOD means high pollution; BOD decreases as treatment progresses.
  4. Settling Tank (Tank 2): Flocs settle as activated (secondary) sludge; the remaining liquid is secondary effluent.
  5. Anaerobic Digestion (Tank 3): Most activated sludge is digested anaerobically, producing biogas (mainly methane). A small portion is recycled as inoculum in Tank 1.
  6. Discharge: Treated secondary effluent, now less polluting, is released into water bodies.

Microbes in Biogas Production

Biogas is a mixture of gases produced by anaerobic digestion of organic waste, mainly containing methane, CO₂, H₂S, and H₂. The major component is methane (50–70%).

• Biogas formation: Depends on the type of organic material and the microbe used.
  • Dough + Saccharomyces cerevisiae: Produces CO₂ as biogas.
  • Cellulose + Methanogens (e.g., Methanobacterium): Produces methane, H₂, and CO₂.
• Biogas plant structure:
  • Concrete tank (10–15 m deep) where slurry (dung + water) is added.
  • Anaerobic digestion occurs, producing biogas collected under a floating cover.
  • Biogas is supplied to households for cooking and lighting.
  • Undigested waste (slurry) is removed and used as fertilizer.
• Development: Biogas plant technology was developed in India by IARI and KVIC.
• Rural importance: Biogas plants are common in rural areas due to abundant cattle dung.

Microbes as Biocontrol Agents

Biocontrol involves using living organisms to control pests and diseases in crops, reducing reliance on chemical pesticides and minimizing environmental pollution.

• Problems with chemical pesticides: Kill both harmful and beneficial organisms, reduce soil fertility, and cause biodiversity loss.
• Biocontrol principle: One organism (natural predator) keeps the population of pests under check without eradicating them, maintaining ecological balance.
• Examples:
  • Ladybird: Controls aphids.
  • Dragonfly: Controls mosquitoes.
  • Bacillus thuringiensis (Bt): Controls butterfly caterpillars in brassica and fruit trees.
  • Trichoderma: Free-living fungus controlling root pathogens.
  • NPV (Nucleopolyhedrovirus): Used as a biocontrol agent.

Microbes as Biofertilizers

Biofertilizers are living organisms that enhance soil nutrient supply, especially nitrogen, reducing the need for chemical fertilizers and preventing pollution.

• Problems with chemical fertilizers: Overuse increases pollution and depletes soil health.
• Types of biofertilizers:
  • Rhizobium: Symbiotic bacteria in root nodules of leguminous plants (e.g., pea), fix atmospheric nitrogen.
  • Azotobacter, Azospirillum: Free-living nitrogen-fixing bacteria in soil.
  • Cyanobacteria (e.g., Anabaena, Nostoc): Possess heterocysts for nitrogen fixation, important in paddy fields.
  • Mycorrhiza: Fungal association with roots of higher plants (e.g., pine), absorbs phosphorus and provides resistance to root pathogens, salinity, and drought. Fungi belong to genus Glomus.

Biofertilizers increase soil fertility and support sustainable agriculture by reducing chemical input and environmental impact.