Microbes in Human Welfare - Class 12 Bihar Board Botany

Microbes in Human Welfare

Microbes play a crucial role in human welfare, impacting food production, environmental management, medicine, and agriculture. Their applications range from sewage treatment and fermentation to antibiotic production and biofertilizer development. Understanding their mechanisms and benefits is essential for exam success, especially in topics like sewage treatment, fermentation, and antibiotics.

Sewage Treatment: Steps and Key Concepts

Sewage treatment involves the removal of contaminants from household waste to prevent river pollution and protect aquatic life. The process is divided into primary, secondary, and tertiary stages, each targeting specific waste components.

• Primary Treatment (Physical/Fizzycal Treatment): -…

Microbes in Human Welfare

Microbes play a crucial role in human welfare, impacting food production, environmental management, medicine, and agriculture. Their applications range from sewage treatment and fermentation to antibiotic production and biofertilizer development. Understanding their mechanisms and benefits is essential for exam success, especially in topics like sewage treatment, fermentation, and antibiotics.

Sewage Treatment: Steps and Key Concepts

Sewage treatment involves the removal of contaminants from household waste to prevent river pollution and protect aquatic life. The process is divided into primary, secondary, and tertiary stages, each targeting specific waste components.

• Primary Treatment (Physical/Fizzycal Treatment):

  • Waste from homes (household waste) contains solids (plastic, glass, stones) and liquids.
  • Waste passes through a Primary Settling Tank where filtration, sedimentation, and separation remove large solids.
  • Remaining water contains soil, pebbles, and organic waste.

• Secondary Treatment (Biological Treatment):

  • Water from the primary tank enters the Aeration Tank.
  • Air (oxygen) is supplied to support aerobic microbes.
  • Flocs form: mesh-like structures of filamentous fungi and aerobic bacteria.
  • Flocs digest organic waste, reducing pollution.

• BOD (Biochemical Oxygen Demand):

  • BOD measures the oxygen required by aerobic microbes to decompose organic matter in 1 liter of water.
  • High BOD indicates high pollution and microbial activity; low BOD means cleaner water.

• Secondary Settling Tank:

  • Water from the aeration tank moves to the secondary tank.
  • Flocs settle as activated sludge; clear water is released to rivers.
  • Some flocs are recycled as inoculum; the rest go to anaerobic digesters.

• Anaerobic Digestion:

  • Activated sludge is transferred to an anaerobic tank containing anaerobic bacteria (e.g., methanogens).
  • Anaerobic bacteria digest sludge, producing biogas (methane, CO₂, H₂S).

• Key Terms:

  • Primary Sludge: Solids settled in the primary tank.
  • Primary Effluent: Liquid moving from primary to aeration tank.
  • Secondary Effluent: Liquid moving from aeration to secondary tank.
  • Activated Sludge: Settled flocs in the secondary tank.
  • Anaerobic Digester: Tank for biogas production.

Fermentation: Mechanism and Applications

Fermentation is an anaerobic process where microbes convert sugars into products like alcohol and lactic acid. It is fundamental in food and beverage industries.

• Respiration and Energy:

  • All living organisms require energy, mainly derived from glucose ($C_6H_{12}O_6$).
  • Glucose undergoes glycolysis to form pyruvic acid (3-carbon compound).

• Fates of Pyruvic Acid:

  • Aerobic Pathway: Pyruvic acid enters Krebs cycle, producing energy.
  • Anaerobic Pathway (Fermentation):
    • Pyruvic acid converts to alcohol (2-carbon, with CO₂ released) or lactic acid (3-carbon).
    • Alcohol formation involves reduction to acetaldehyde, then to ethanol.

• Microbes Used:

  • Yeast (Saccharomyces cerevisiae): Used in bread (baker’s yeast) and alcohol (brewer’s yeast) production.
  • Lactic Acid Bacteria (LAB): Used in curd/yogurt formation.

• Bread and Alcohol:

  • Yeast ferments sugars, producing CO₂ and alcohol.
  • CO₂ causes bread to rise and become porous; alcohol evaporates during baking.

• Alcoholic Beverages:

  • Non-distilled (Fermented) Drinks: Produced only by fermentation; alcohol content ≤ 13–15%. Examples: beer, wine, toddy, cider.
  • Distilled Drinks: Alcohol content > 13–15%, achieved by distillation (separating alcohol by boiling and condensing). Examples: whisky, rum, brandy, vodka, gin.

• Distillation Principle:

  • Alcohol boils at 78.3°C (lower than water).
  • Vapors are condensed and collected to increase alcohol concentration.

Curd, Yogurt, and Cheese Formation

Microbes are essential in transforming milk into curd, yogurt, and cheese, enhancing nutritional value and digestibility.

• Curd Formation:

  • Warm milk is inoculated with a small amount of curd (inoculum).
  • Lactobacillus (LAB): Converts lactose (milk sugar) into lactic acid.
  • Lactic acid coagulates milk protein (casein), forming curd.
  • Curd is rich in vitamin B12 and is easier to digest than milk.

• Yogurt Formation:

  • Milk is boiled at 80–90°C, cooled to room temperature.
  • 1–2% curd is added and incubated for 16–18 hours or stored at 5°C.

• Cheese Formation:

  • Milk is converted to curd, then ripened to develop taste, texture, and aroma.
  • Swiss Cheese: Made by Propionibacterium; holes (pores) form due to CO₂ release.
  • Roquefort Cheese: Made by Penicillium roqueforti; known for flavor and aroma.

Industrial Production of Organic Acids and Enzymes

Microbes are used to produce organic acids and enzymes on a large scale for food, detergents, and pharmaceuticals.

• Organic Acids:

  • Ethanol: Produced by yeast.
  • Acetic Acid: Produced by Acetobacter aceti; used in vinegar.
  • Citric Acid: Produced by Aspergillus niger; used in soft drinks.
  • Lactic Acid: Produced by Lactobacillus; used in dairy.

• Microbial Enzymes:

  • Protease: Used in detergents and meat softening.
  • Lipase: Used in detergents.
  • Amylase: Used in baking and brewing.
  • Pectinase: Used for juice clarification.

Antibiotics: Discovery and Types

Antibiotics are substances produced by microbes to inhibit or kill bacteria, revolutionizing medicine.

• Discovery:

  • Alexander Fleming (1928): Discovered penicillin from Penicillium notatum (a fungus) while studying Staphylococcus bacteria.
  • Penicillin killed bacteria near the fungus, leading to its use as an antibiotic.

• Development:

  • Chain and Florey: Modified and enhanced penicillin’s use.
  • Fleming, Chain, and Florey received the Nobel Prize in 1945 for their contributions, especially during World War II.

• Key Points:

  • Antibiotics are effective only against bacterial infections, not viral.
  • Common antibiotics: Penicillin, Kanamycin, Chloramphenicol, Ampicillin, Tetracycline.

Microbes in Agriculture: Biofertilizers and Biocontrol Agents

Microbes improve soil fertility and protect crops from pests, reducing reliance on chemical fertilizers and pesticides.

• Biofertilizers:

  • Rhizobium: Symbiotic nitrogen fixation in leguminous plants.
  • Azotobacter: Free-living nitrogen fixation.
  • Cyanobacteria (Anabaena, Nostoc): Nitrogen fixation in rice fields.

• Mycorrhiza:

  • Symbiotic association between higher plants (e.g., Pinus) and fungi (Glomus) in roots.
  • Enhances phosphorus absorption, water stress tolerance, and disease resistance.

• Biocontrol Agents:

  • Bacillus thuringiensis (Bt): Produces Cry toxin (crystal toxin) for pest resistance in crops like cotton and corn.
  • Cry genes (Cry1AC, Cry2AB) protect against bollworm and corn borer.
  • Trichoderma: Suppresses root pathogens.
  • Predators: Ladybird beetles control aphids; dragonflies control mosquitoes.

Microbes in Food Industry: Key Examples

Microbes are integral to the production of various foods, enhancing taste, texture, and nutritional value.

• Bread: Yeast ferments sugar, producing CO₂ and alcohol; CO₂ makes bread soft and porous.
• Idli/Dosa: Fermentation by yeast and bacteria produces CO₂, making them soft and digestible.
• Toddy (Tadi): Sap from palm trees ferments naturally due to yeast, producing an alcoholic drink; alcohol content increases with time and temperature.
• Cheese: Microbial action develops flavor, texture, and aroma; Swiss cheese holes are due to CO₂.

Exam-Focused Takeaways and PYQ Highlights

Several points are frequently tested in exams and should be memorized for high recall.

• Primary Treatment: Physical removal of solids; screening, filtration, sedimentation.
• Secondary Treatment: Biological removal of organic matter; aerobic bacteria (flocs) digest waste.
• BOD: Directly proportional to pollution; high BOD means high pollution.
• Activated Sludge: Settled flocs; transferred to anaerobic digesters for biogas production.
• Fermentation: Anaerobic conversion of sugars to alcohol/lactic acid; yeast and LAB are key microbes.
• Distilled vs. Non-distilled Alcohol: Non-distilled ≤ 13–15% alcohol; distilled > 13–15% via distillation.
• Curd Formation: Lactobacillus converts lactose to lactic acid, coagulating casein.
• Cheese Types: Swiss (Propionibacterium, CO₂ holes), Roquefort (Penicillium roqueforti, flavor).
• Antibiotics: Penicillin (Fleming), Chain, Florey; only for bacterial infections.
• Biofertilizers: Rhizobium (symbiotic), Azotobacter (free-living), Cyanobacteria (rice fields).
• Biocontrol: Bt (Cry toxin), Trichoderma, ladybird beetle, dragonfly.
• Mycorrhiza: Glomus with higher plants; improves phosphorus and water uptake.
• Microbial Enzymes: Protease, lipase, amylase, pectinase for industrial use.

Table: Distilled vs. Non-distilled Alcoholic Beverages

Key MCQ Points:

• Primary treatment = physical, secondary = biological.
• Flocs = mesh of filamentous fungi + aerobic bacteria.
• BOD is not biological oxygen demand, but biochemical oxygen demand.
• Swiss cheese holes are due to CO₂ release by Propionibacterium.
• Penicillin is the first antibiotic, discovered by Fleming from Penicillium notatum.
• Rhizobium fixes nitrogen in leguminous plants; Azotobacter is free-living.
• Bt Cry genes confer pest resistance in cotton and corn.