🌸Chapter 8
Microbes in Human Welfare
(4 Marks)
1. Explain the role of microbes in
the household products.
Answer:
Microbes are used in several household products:
1.
Curd – Lactobacillus converts
lactose into lactic acid, coagulating milk.
2.
Bread – Saccharomyces cerevisiae
(yeast) ferments dough → CO₂ makes bread fluffy.
3.
Beverages – Saccharomyces cerevisiae
ferments sugars to produce alcohol in beer, wine.
4.
Cheese – Lactobacillus and Penicillium
roqueforti help in flavor and texture formation.
2. Describe the role of microbes in
industrial production.
Answer:
Microbes produce various valuable products:
- Alcoholic beverages – Saccharomyces cerevisiae.
- Organic acids – Aspergillus niger →
citric acid; Acetobacter aceti → acetic acid.
- Enzymes – Aspergillus →
amylase; Bacillus → protease.
- Antibiotics – Penicillium notatum →
penicillin.
These are produced in large bioreactors under controlled conditions.
3. What is fermentation? Explain
with industrial examples.
Answer:
Fermentation is the anaerobic conversion of sugar into alcohol or acids by
microbes.
Examples:
- Saccharomyces cerevisiae → sugar → ethanol (in brewing
industry).
- Acetobacter aceti → ethanol → acetic acid
(vinegar).
- Aspergillus niger → sugar → citric acid.
Fermentation is used in making wine, beer, and vinegar.
4. Explain the discovery and
importance of Penicillin.
Answer:
- Discovered by Alexander
Fleming in 1928 from Penicillium notatum.
- Chain and Florey developed it for mass
production.
- It was the first true
antibiotic, saved millions of lives during World War II.
- Effective against Gram-positive
bacteria by inhibiting cell wall synthesis.
5. Describe the steps of sewage
treatment.
Answer:
1.
Primary
treatment:
o Physical removal of large particles
by filtration and sedimentation.
2.
Secondary
treatment:
o Biological process using aerobic
microbes.
o Aeration tank → microbes oxidize organic
matter → activated sludge.
3.
Sludge
digestion:
o Anaerobic microbes digest sludge →
produce biogas.
4.
Effluent
discharge:
o Treated water released into rivers
or reused.
6. Explain the role of microbes in
sewage treatment plants.
Answer:
- Aerobic bacteria oxidize
organic matter → CO₂, H₂O.
- Forms activated sludge,
which settles and is partly reused.
- Anaerobic microbes in digesters
break down sludge → biogas (methane, CO₂).
- Reduces organic load and
prevents water pollution.
7. What is biogas? Describe its composition
and production process.
Answer:
Biogas is a methane-rich fuel produced by anaerobic digestion of organic
waste.
- Composition: 50–70% CH₄, 30–40%
CO₂, and traces of H₂S.
Process:
1.
Slurry
of cow dung + water fed into digester.
2.
Anaerobic
microbes (methanogens like Methanobacterium) decompose it.
3.
Biogas
collected from the dome and used as fuel.
8. Explain the working of a biogas
plant.
Answer:
1.
Mixing
tank – Cow dung + water slurry prepared.
2.
Digester
tank – Anaerobic bacteria break down
organic matter.
3.
Gas
holder – Biogas
accumulates in dome.
4.
Outlet – Used slurry removed and used as
manure.
Biogas contains methane and is used for cooking and lighting.
9. What are methanogens? Where are
they found and what are their uses?
Answer:
- Methanogens are anaerobic
archaebacteria producing methane gas.
- Example: Methanobacterium.
- Found in:
- Rumen of cattle → digest
cellulose.
- Anaerobic digesters in sewage
plants → produce biogas.
- Used for waste management and
renewable energy.
10. Explain how microbes are useful
in biogas production and biocontrol.
Answer:
- Biogas: Methanobacterium
decomposes organic waste → methane.
- Biocontrol: Trichoderma fungi kill
soil pathogens; Bacillus thuringiensis kills pests.
Both methods are eco-friendly and reduce chemical usage.
11. Describe the different types of
biofertilizers and their roles.
Answer:
1.
Symbiotic
nitrogen fixers
– Rhizobium in legume root nodules.
2.
Free-living
nitrogen fixers
– Azospirillum, Azotobacter.
3.
Cyanobacteria – Anabaena, Nostoc, Oscillatoria
(in paddy fields).
4.
Mycorrhizae – Fungal associations aiding
phosphorus absorption.
12. Differentiate between chemical
fertilizers and biofertilizers.
|
Chemical Fertilizers |
Biofertilizers |
|
Inorganic salts providing NPK. |
Living microbes improving fertility. |
|
Quick effect but temporary. |
Slow but sustainable. |
|
Cause soil and water pollution. |
Eco-friendly and renewable. |
13. Explain the role of microbes as
biofertilizers in agriculture.
Answer:
- Rhizobium fixes nitrogen in legumes.
- Azotobacter and Azospirillum fix
nitrogen freely in soil.
- Anabaena in Azolla enriches
paddy fields.
- Mycorrhiza increases phosphate
absorption.
→ Improves soil fertility and reduces chemical use.
14. What is bio-control? Describe
with examples.
Answer:
Use of living organisms to control pests and plant diseases.
Examples:
- Bacillus thuringiensis → kills insect larvae (Bt
cotton).
- Trichoderma → controls soil pathogens.
- Ladybird beetles → feed on aphids.
Eco-friendly alternative to pesticides.
15. Explain how Bacillus
thuringiensis helps in pest control.
Answer:
- Produces Cry toxin
protein crystals.
- When ingested by insects, toxin
binds gut lining → forms pores → cell death.
- Used in sprays and Bt cotton
for caterpillar control.
16. How are microbes used in organic
farming?
Answer:
- Uses Rhizobium, Azospirillum,
Anabaena as biofertilizers.
- Trichoderma, Bt as biocontrol
agents.
- Avoids chemical
fertilizers/pesticides → sustainable farming.
- Improves soil structure and
fertility.
17. Describe the role of microbes in
industrial enzyme production.
Answer:
- Microbes secrete enzymes used
in industries:
- Amylase → starch hydrolysis.
- Lipase → detergents and food
processing.
- Pectinase → fruit juice clarification.
- Protease → leather and textile
industries.
18. What is a bioreactor? Describe
its function.
Answer:
- Large vessel for large-scale
microbial product synthesis.
- Provides optimal conditions:
temperature, pH, aeration, agitation.
- Has inlet for nutrients, air
supply, pH sensors, and outlet for product.
- Used in production of
antibiotics, enzymes, alcohol.
19. What is an antibiotic? Name some
important examples and their uses.
Answer:
- Chemical substances that
destroy/inhibit other microbes.
Examples:
1.
Penicillin
– Penicillium notatum – antibacterial.
2.
Streptomycin
– Streptomyces griseus – TB treatment.
3.
Tetracycline
– Streptomyces aureofaciens – broad-spectrum.
20. Write a short note on Rhizobium
and Anabaena.
Answer:
- Rhizobium: Symbiotic nitrogen fixer in
legumes; forms nodules.
- Anabaena: Cyanobacterium; fixes
nitrogen independently or symbiotically with Azolla.
Both enrich soil with nitrogen, improving fertility naturally.
21. What is the significance of
microbes in waste management?
Answer:
- Microbes decompose organic
waste in compost pits.
- Sewage treatment plants use
bacteria to remove organic matter.
- Methanogens produce biogas from
waste.
- Reduce pollution and recycle
nutrients.
22. Describe the process of
secondary sewage treatment.
Answer:
1.
Sewage
passed into aeration tank.
2.
Air
pumped → promotes growth of aerobic microbes.
3.
Organic
matter oxidized → CO₂ + H₂O.
4.
Activated
sludge formed → settled → some reused; rest digested anaerobically.
23. Explain the role of microbes in
the dairy industry.
Answer:
- Lactobacillus and Streptococcus
convert milk → curd, yogurt.
- Propionibacterium sharmanii → Swiss cheese (holes).
- Penicillium roqueforti → blue cheese flavor.
- Improve texture, flavor, and
digestibility.
24. Name the microbes involved in
the production of:
(a) Wine
(b) Cheese
(c) Citric acid
(d) Curd
Answer:
(a) Saccharomyces cerevisiae
(b) Lactobacillus, Penicillium roqueforti
(c) Aspergillus niger
(d) Lactobacillus bulgaricus
25. How is organic waste converted
into energy by microbes?
Answer:
- Anaerobic bacteria digest waste
in biogas plants → produce methane (biogas).
- Methanogens like Methanobacterium
act on cow dung, sewage sludge.
- Biogas used as renewable fuel;
residue → manure.
26. What is the function of the
activated sludge in sewage treatment?
Answer:
- Contains aerobic microbes that
oxidize organic matter.
- Used as inoculum for further
treatment.
- Remaining sludge digested
anaerobically to generate biogas.
27. How do microbes help in retting
of jute and flax?
Answer:
- Clostridium species decompose pectins
binding fibers to stem.
- Loosens fibers for easy
extraction.
- Essential for jute/flax fiber
processing.
28. Discuss the uses of microbes in
the pharmaceutical industry.
Answer:
- Antibiotics: Penicillin,
Streptomycin.
- Vaccines: Produced using
attenuated microbes.
- Enzymes: Proteases and lipases
for drug synthesis.
- Vitamins: B₁₂, riboflavin
produced by bacteria.
29. Why are antibiotics ineffective
against viruses?
Answer:
- Viruses lack cell walls and
metabolic machinery.
- Antibiotics target bacterial
processes like protein/cell wall synthesis.
- Hence, they cannot act on
viruses.
30. What are single-cell proteins
(SCP)? How are they beneficial?
Answer:
- Microbial biomass rich in
protein used as food.
- Example: Spirulina, Methylophilus
methylotrophus.
Benefits: - High protein yield.
- Rich in vitamins/minerals.
- Useful for malnutrition
control.
31. Explain the importance of
cyanobacteria in agriculture.
Answer:
- Anabaena, Nostoc, Oscillatoria
fix atmospheric nitrogen.
- Increase soil fertility in
paddy fields.
- Used as biofertilizers and
reduce chemical fertilizer need.
32. What is the importance of Azolla-Anabaena
association in rice fields?
Answer:
- Azolla (water fern) hosts Anabaena
(cyanobacteria).
- Anabaena fixes nitrogen, enriching soil
naturally.
- Used as green manure in paddy
cultivation.
33. What are probiotics? Mention
their benefits.
Answer:
- Live beneficial microbes
improving gut health.
- Example: Lactobacillus
acidophilus.
Benefits: - Boost immunity.
- Prevent diarrhea, improve
digestion.
- Suppress harmful gut microbes.
34. How does Trichoderma act
as a bio-control agent?
Answer:
- Fungus living in plant root
ecosystems.
- Produces antifungal metabolites
that suppress pathogens.
- Used in seed and soil
treatments for crop protection.
35. Describe the role of microbes in
food and beverage industries.
Answer:
- Yeast → beer, wine.
- Lactobacillus → yogurt, curd.
- Aspergillus oryzae → soy sauce.
- Acetobacter → vinegar.
Enhances taste, flavor, and preservation.
36. Explain how antibiotics are
produced on a large scale.
Answer:
- Grown in large fermenters with
nutrient medium.
- Microbes produce antibiotic
during stationary phase.
- Extracted, purified, and
processed into medicines.
37. How do microbes contribute to
soil fertility?
Answer:
- Fix nitrogen (e.g., Rhizobium,
Azotobacter).
- Decompose organic matter →
humus formation.
- Release nutrients (phosphorus,
sulfur) for plant uptake.
38. What is the use of Aspergillus
niger in industries?
Answer:
- Produces citric acid (food
preservative).
- Secretes enzymes like amylase
and pectinase.
- Used in beverage and detergent
industries.
39. How do microbes help in
bioremediation?
Answer:
- Microbes degrade toxic
pollutants.
- Pseudomonas breaks down petroleum.
- Used in oil spill cleanup and
waste treatment.
40. Write short notes on microbial
enzymes used in industry.
Answer:
- Amylases: break starch (food/textile).
- Lipases: used in detergents.
- Pectinases: juice clarification.
- Proteases: used in leather/textiles.
41. How are microbes useful in the
textile industry?
Answer:
- Amylase → starch removal from fabric.
- Protease → softens silk and wool.
- Pectinase → retting of fibers.
42. Describe the role of microbes in
alcohol production.
Answer:
- Yeast (Saccharomyces
cerevisiae) ferments sugar → ethanol + CO₂.
- Used in wine, beer, whiskey
industries.
- Anaerobic process in
fermentation tanks.
43. What are the advantages of using
biofertilizers in agriculture?
Answer:
- Eco-friendly and non-polluting.
- Improve soil structure and
fertility.
- Cost-effective and sustainable.
- Promote long-term yield
stability.
44. Describe the working of a
typical biogas plant with labeled parts.
Answer:
1.
Mixing
tank (cow dung + water).
2.
Digester
(anaerobic microbes act).
3.
Gas
holder (stores methane).
4.
Outlet
(for digested slurry).
Methane used as fuel; slurry as manure.
45. Explain how microbes are used in
the production of citric acid and vinegar.
Answer:
- Citric acid: Aspergillus niger
ferments sugar.
- Vinegar: Acetobacter aceti
oxidizes ethanol → acetic acid.
Used in food and beverage industries.
46. Describe the importance of Trichoderma
and Bacillus thuringiensis in agriculture.
Answer:
- Trichoderma – controls soil fungi
(biofungicide).
- Bt – insecticidal protein kills
caterpillars.
Both are eco-friendly alternatives to chemicals.
47. Write the principle behind
biogas production.
Answer:
- Anaerobic digestion of organic
waste by methanogens.
- Converts biomass into
methane-rich gas.
- Methane used as renewable
energy source.
48. How do microbes help in
improving the quality of curd and cheese?
Answer:
- Lactobacillus ferments lactose → lactic acid
→ curd formation.
- Propionibacterium and Penicillium enhance
cheese flavor and texture.
49. What are the uses of fungi in
industry?
Answer:
- Penicillium → antibiotics.
- Aspergillus niger → citric acid.
- Trichoderma → biofungicide.
- Saccharomyces cerevisiae → alcohol production.
50. Describe the process and
advantages of biogas production.
Answer:
- Cow dung + water → anaerobic
digestion by Methanobacterium.
- Produces methane-rich gas for
cooking and lighting.
Advantages:
1.
Renewable
energy source.
2.
Reduces
waste.
3.
Provides
organic manure.
