Microbes in Human Welfare — Part 1: Microbes at home and in industry: visual lesson, ISC Class 12 Biology

Lesson

Useful microbes

Part 1 — the bacteria and fungi that make our curd, bread and cheese, and the medicines and chemicals of industry.

In this lesson you will

Explain the role of Lactobacillus, Saccharomyces and Propionibacterium in household products
Name microbes used to make beverages, antibiotics, organic acids, alcohol and enzymes
State the sources and uses of streptokinase, cyclosporin A and statins

Concept

Microbes in household products

Fermentation by microbes changes the taste, texture and nutritive value of food.

Table of household products and the microbes that make them
Product	Microbe	What it does
Curd	Lactobacillus (lactic acid bacteria)	Makes lactic acid that coagulates and partly digests milk proteins; adds vitamin B12
Bread	Saccharomyces cerevisiae (baker’s yeast)	Ferments sugar in dough; carbon dioxide makes it rise
Idli and dosa batter	Bacteria	Fermentation; carbon dioxide puffs the batter
Toddy	Yeasts and bacteria	Ferments palm sap
Swiss cheese	Propionibacterium sharmanii	Large holes from carbon dioxide
Roquefort cheese	Specific fungi	Ripening and flavour

Diagram

How milk becomes curd

Lactobacillus and other lactic acid bacteria (LAB) multiply in warm milk and make lactic acid. The pH falls from about 6.57 to about 4.41, and milk proteins coagulate.

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