Class 12 Biology — Chapter 8: MICROBES IN HUMAN WELFARE

Understand the role of microbes like Lactic Acid Bacteria (LAB) in converting milk to curd, and the function of yeast (Saccharomyces cerevisiae) in fermenting dough for bread, idli, and dosa. This also includes the use of specific bacteria and fungi in the production of different types of cheese, such as Swiss cheese and Roquefort cheese.

Learn how yeast, specifically Saccharomyces cerevisiae (brewer's yeast), is used in large industrial vessels called fermentors to produce alcoholic beverages like wine, beer, whisky, and rum from malted cereals and fruit juices. Differentiate between drinks produced with and without distillation.

Define antibiotics as chemical substances produced by microbes that inhibit the growth of other microbes. Understand the story of the first antibiotic, Penicillin, discovered by Alexander Fleming from the fungus Penicillium notatum, and how its potential was later established by Chain and Florey.

Identify specific microbes used for the commercial production of organic acids (e.g., Aspergillus niger for citric acid), enzymes (e.g., lipases, streptokinase), and other bioactive molecules like Cyclosporin A (immunosuppressant from Trichoderma polysporum) and Statins (cholesterol-lowering agents from Monascus purpureus).

Describe the process of treating municipal wastewater (sewage) in Sewage Treatment Plants (STPs). Differentiate between primary treatment (physical removal of solids) and secondary or biological treatment, which uses aerobic microbes in 'flocs' to reduce the Biochemical Oxygen Demand (BOD) of the water.

Understand the process of treating the sediment ('activated sludge') from secondary treatment. Learn how anaerobic bacteria in large 'anaerobic sludge digesters' break down the organic matter, producing biogas (a mixture of methane, hydrogen sulphide, and carbon dioxide) as a useful byproduct.

Recognize the diversity of the microbial world, which includes bacteria, fungi, protozoa, viruses, viroids, and prions. Understand that microbes are ubiquitous, found even in extreme environments like thermal vents and deep snow, and can be cultured in labs to form visible colonies.