# Microbes in Human Welfare Notes, Class 12 Biology | SwaVid Microbes in Human Welfare, NCERT Class 12 Biology: notes with key ideas, key terms, common mistakes and 3 quick checks with worked answers. Canonical: https://www.swavid.com/cbse/class-12/biology/chapter/microbes-in-human-welfare Source: https://www.swavid.com/cbse/class-12/biology/chapter/microbes-in-human-welfare # Microbes in Human Welfare ## Key terms ## Key ideas ## Common mistakes ## Quick checks ## Keep going ## Questions parents ask ## Class 12 Biology on SwaVid ### Microbes in household products ### Microbes in industrial products ### Microbes in sewage treatment ### Microbes in biogas production ### Microbes as biocontrol agents ### Microbes as biofertilisers ### Next chapter ### Related chapter ### Related chapter ### Related chapter ### All chapters SwaVid › CBSE › Class 12 › Biology › Microbes in Human Welfare Notes written by SwaVid from the NCERT textbook. Class 12 Biology, Chapter 8. Key ideas, formulas and common mistakes. CBSE prints 12 marks for Unit VIII, not for this chapter alone. Short answer. This chapter describes the diverse beneficial roles played by microorganisms in daily household products, industrial processes, sewage treatment, biogas production, and pest management. It demonstrates that not all microbes are harmful pathogens, and many are essential tools for human welfare and ecological balance. Source: NCERT Biology (Reprint 2026-27) , Chapter 8, Microbes in Human Welfare Lactic acid bacteria convert milk to curd and improve its nutritional quality by increasing vitamin B12. Yeasts like Saccharomyces cerevisiae ferment dough for bread, while bacteria ferment dough for traditional foods such as idli and dosa. Industrial production uses large vessels called fermentors to grow microbes. Saccharomyces cerevisiae produces fermented beverages, while other microbes yield antibiotics like penicillin, organic acids, enzymes such as lipases and pectinases, and bioactive molecules like cyclosporin A and statins. Sewage treatment involves physical primary treatment and biological secondary treatment. Aerobic microbes in aeration tanks consume organic matter and lower biological oxygen demand, followed by anaerobic digestion of activated sludge, which produces biogas. Methanogens, mainly Methanobacterium, break down cellulosic material anaerobically inside biogas plants. They produce a flammable mixture of gases containing mostly methane, carbon dioxide, and hydrogen, using cattle dung as an input. Biocontrol uses biological organisms to reduce pest populations instead of toxic chemical pesticides. Examples include Bacillus thuringiensis against butterfly caterpillars, Trichoderma fungus against plant pathogens, and species-specific baculoviruses of the genus Nucleopolyhedrovirus. Biofertilisers enrich the nutrient quality of the soil using living organisms. Key examples include nitrogen-fixing bacteria such as Rhizobium, Azotobacter, and Azospirillum, mycorrhizal fungi of the genus Glomus, and cyanobacteria such as Anabaena, Nostoc, and Oscillatoria. Try each question first. Then tap it to see the answer. BOD is directly proportional to the amount of biodegradable organic matter in water. A decrease in BOD from 400 mg L⁻¹ to 40 mg L⁻¹ means there is a corresponding sharp decline in organic matter. This reduction indicates that microbial digestion was successful and the water is significantly less polluted. It indicates a major reduction in organic matter and water pollution. The clot buster used to dissolve clots inside blood vessels is streptokinase. Streptokinase is naturally produced by the bacterium Streptococcus and then modified by genetic engineering. Streptokinase, produced by Streptococcus The chapter identifies baculoviruses belonging to the genus Nucleopolyhedrovirus. They are species-specific, narrow-spectrum insecticidal pathogens. They show no negative impacts on plants, mammals, birds, fish, or non-target insects. Nucleopolyhedrovirus; desirable because they have narrow-spectrum, species-specific action without harming non-target organisms. Biotechnology: Principles and Processes . Human Health and Disease . Biotechnology and its Applications . Ecosystem . The 13 chapters of Class 12 Biology . CBSE does not give marks to one chapter. It prints 12 marks for Unit VIII, Biology and Human Welfare, which includes Microbes in Human Welfare. No. They are written by SwaVid from the NCERT textbook. The CBSE curriculum is the reference for what is assessed. Biotechnology: Principles and Processes. SwaVid is an AI tutor for Indian students in Classes 6 to 12. It finds the earlier ideas a child missed, then teaches today’s chapter. Start free to see how it works. - Ch 8 NCERT book - 12 marks, Unit VIII - 3 quick checks - Confusing the biological sources of cyclosporin A and statins . Remember that cyclosporin A is produced by the fungus Trichoderma polysporum, while statins are produced by the yeast Monascus purpureus. - Assuming high BOD indicates clean water . BOD measures organic pollution. A higher BOD value means more organic matter is present and the water is more polluted. - Mixing up primary treatment and secondary treatment in sewage processing . Primary treatment is strictly a physical removal of particles through filtration and sedimentation, whereas secondary treatment is biological and involves microbial degradation. - Calling ladybirds and dragonflies microbes . Ladybirds and dragonflies are useful biocontrol agents mentioned in the chapter, but they are predatory insects, not microorganisms. ## Key Links - [CBSE](https://www.swavid.com/cbse) - [Class 12](https://www.swavid.com/cbse/class-12) - [Biology](https://www.swavid.com/cbse/class-12/biology/chapters) - [Start free →](https://www.swavid.com/signup) - [All 13 chapters](https://www.swavid.com/cbse/class-12/biology/chapters) - [NCERT Biology (Reprint 2026-27)](https://ncert.nic.in/textbook.php) - [Open notes](https://www.swavid.com/cbse/class-12/biology/chapter/biotechnology-principles-and-processes) - [Open notes](https://www.swavid.com/cbse/class-12/biology/chapter/human-health-and-disease) - [Open notes](https://www.swavid.com/cbse/class-12/biology/chapter/biotechnology-and-its-applications) - [Open notes](https://www.swavid.com/cbse/class-12/biology/chapter/ecosystem) - [Class 12 Biology](https://www.swavid.com/cbse/class-12/biology/chapters) - [Start free →](https://www.swavid.com/signup)