Learning objectives

Learning objectives ➢ Differentiates probiotics from pathogens. ➢ Understands the use of microbes in household products. ➢ Learns about antibiotic production and fermented beverages. ➢ Realizes the importance of microbes in sewage treatment and energy generation. ➢ Realizes the applications of microbes in bio-remediation. XII Std Biology-Zoology Chapter- XII Std Biology-Zoology Chapter- Microbes in Human Welfare temperature (≤ o C) multiply and convert milk into curd. Curd is more nutritious than milk as it contains a number of organic acids and vitamins. Prebiotics are compounds in food (fibers) that induce the growth or activity of beneficial microorganisms. Probiotics are live microorganisms intended to provide health benefits when consumed, generally by improving or restoring the gut flora. Yogurt is produced by bacterial fermentation of milk, and lactic acid is produced as a byproduct. Microorganisms such as Streptococcus thermophilus and Lactobacillus bulgaricus coagulate the milk protein and convert the lactose in the milk to lactic acid. The flavour in yogurt is due to acetaldehyde. Cheese is a dairy product produced in a wide range of flavours, textures and is formed by coagulation of the milk protein, casein. During cheese production, milk is usually acidified and the enzyme rennet is added to cause coagulation. The solids are separated and pressed to form cheese. Most cheese are made with a starter bacteria, Lactococcus , Lactobacillus or Streptococcus. Paneer (cottage cheese) is fresh cheese common in South Asia, especially in India. It is made by curdling milk with lemon juice, vinegar and other edible acids. Large holes in Swiss cheese is due to the production of large amount of carbon-di-oxide by the bacterium Propionibacterium shermanii. The dough used in the preparation of idlis and dosas are fermented by the bacteria Leuconostoc mesenteroides whereas the dough used in bread making is fermented by Saccharomyces cerevisiae (Baker’s Yeast). Fermentation of glucose mainly forms ethyl alcohol and carbon- di-oxide, which is responsible for leavening of dough. When leavened dough is baked, both carbon-di-oxide and ethyl alcohol evaporate making the bread porous and soft.