Short Notes: Microbes in Human Welfare

Table of Contents
1. Microbes in Household Products
2. Industrial Products
3. Sewage Treatment
4. Biogas
5. Biofertilisers
6. Biopesticides
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Microbes in Household Products

Microorganisms are used in several everyday household products by converting raw materials into useful foods and beverages through fermentation. These processes are safe, economically viable and part of traditional food technology.

• Lactic acid bacteria (LAB) - Lactobacillus: convert lactose in milk into lactic acid to form curd and are involved in cheese production by acidification, flavour and texture development; mechanism: lactic acid fermentation (anaerobic glycolysis).
• Baker's yeast - Saccharomyces cerevisiae: used in bread making; ferments sugars to produce carbon dioxide (CO₂) that causes the dough to rise (leavening) and small amounts of alcohol and flavour compounds.
• Brewer's yeast - strains of Saccharomyces: used in production of alcoholic beverages (beer, wine); ferment sugars to produce ethanol and CO₂ under controlled conditions.

Industrial Products

Microbes are essential in industrial biotechnology where controlled fermentation yields chemicals, enzymes and pharmaceuticals. Large-scale production typically uses submerged or solid-state fermentation in bioreactors.

• Organic acids: Citric acid production by Aspergillus niger (used in food, pharmaceuticals and cleaning agents); Acetic acid production involves Acetobacter (vinegar formation).
• Enzymes: microbial lipases, proteases and amylases are produced industrially for use in detergents, food processing, leather and textile industries.
• Antibiotics: antibiotic compounds produced by microbes include penicillin (from Penicillium species) and streptomycin (from Streptomyces); these are isolated and purified for therapeutic use.

Sewage Treatment

Sewage treatment uses physical, chemical and biological methods to remove suspended solids, organic matter and pathogens from wastewater so that treated water can be safely discharged or reused. Microbial action is central to the biological stage.

• Primary treatment: physical processes such as screening, sedimentation and removal of grit and large particles to reduce suspended solids.
• Secondary treatment: biological degradation of dissolved and suspended organic matter by microbes. Common processes include activated sludge systems (aerobic bacteria metabolise organic matter), trickling filters and oxidation ponds.
• Anaerobic processes: carried out in absence of oxygen by anaerobic bacteria and methanogens; these convert organic matter to biogas containing methane and carbon dioxide and reduce sludge volume.
• Methanogens (e.g., Methanobacterium): produce biogas (mainly CH₄ and CO₂) during anaerobic digestion; sulphate-reducing bacteria can contribute H₂S in some systems.
• Tertiary treatment: advanced removal of nutrients (nitrogen and phosphorus), heavy metals and disinfection (chlorination, UV) to meet discharge standards and reduce pathogens.

Biogas

Biogas is a renewable fuel produced by anaerobic digestion of organic wastes by a consortium of microorganisms. It is used for cooking, heating, electricity generation and as vehicle fuel after upgrading.

• Microbes involved: hydrolytic and fermentative bacteria break down complex polymers; acidogenic and acetogenic bacteria convert products into acetate, H₂ and CO₂; methanogens (e.g., Methanobacterium) form methane from acetate, H₂ and CO₂.
• Feedstock: cattle dung, poultry litter, crop residues, kitchen waste and sewage sludge are commonly used in biogas plants.
• Stages of anaerobic digestion: hydrolysis → acidogenesis → acetogenesis → methanogenesis.
• Components: methane (major combustible component), carbon dioxide and small amounts of hydrogen and other gases; raw biogas may contain H₂S and water vapour and normally requires cleaning before utilisation.
• By-products and uses: nutrient-rich bio-slurry from the digester is used as organic fertilizer; biogas replaces fossil fuels and reduces greenhouse gas emissions when used instead of firewood, kerosene or LPG.

Biofertilisers

Biofertilisers are preparations containing living microorganisms that, when applied to seed, plant surfaces or soil, colonise the rhizosphere or the interior of the plant and promote growth by increasing the supply or availability of primary nutrients.

• Nitrogen fixers: Rhizobium (forms root nodules on legumes; symbiotic nitrogen fixation), Azotobacter and Azospirillum (free-living nitrogen-fixing bacteria) convert atmospheric N₂ into ammonia usable by plants.
• Cyanobacteria: genera such as Nostoc and Anabaena fix atmospheric nitrogen and are used in paddy fields and degraded soils to improve fertility.
• Mycorrhiza: symbiotic association between fungal hyphae and plant roots that increases surface area for water and phosphorus uptake and enhances resistance to some pathogens.
• Benefits and application: biofertilisers reduce dependency on chemical fertilisers, improve soil health and are applied as seed inoculants, root dips or soil additions according to crop-specific recommendations.

Biopesticides

Biopesticides are formulations of living organisms or their products used to control pests, weeds or diseases. They are typically target-specific and environmentally safer than many chemical pesticides.

• Bacillus thuringiensis (Bt): produces proteinaceous Cry (Bt) toxins that are toxic to specific insect larvae when ingested; widely used in spray formulations and genetically engineered crops for pest control.
• Trichoderma: fungal biocontrol agent that suppresses soil-borne plant pathogens by parasitism, competition and production of antifungal metabolites; used in seed treatments and soil amendments.
• Nucleopolyhedrovirus (NPV): insect-specific viruses used against lepidopteran pests; highly species-specific and safe to non-target organisms including humans.
• Advantages: target specificity, reduced environmental persistence, compatibility with integrated pest management (IPM) and safety for beneficial organisms and human health.

Summary: Microbes contribute to human welfare through food production (curd, bread, alcoholic beverages), industrial manufacture of acids, enzymes and antibiotics, treatment and recycling of waste (sewage treatment, biogas), enhancement of soil fertility (biofertilisers) and eco-friendly pest control (biopesticides). Understanding the organisms, mechanisms and applications helps optimise these processes for sustainable agriculture, industry and domestic use.