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Home/Practice questions/Biology
BiologyMicrobes in Human Welfare

Lactic acid bacteria (LAB) convert milk to curd. They also improve th…

Read the given passage and answer the following question:

Microbes like Saccharomyces cerevisiae are utilised in the commercial production of ethanol. Enzyme production is another application of microbes, with lipases being used in detergent formulations to effectively remove oily stains from laundry. It is common to observe that commercially bottled fruit juices appear clearer compared to homemade ones, as the former undergo clarification processes employing pectinases and proteases. Streptokinase, produced by the bacterium Streptococcus and genetically modified, serves as a "clot buster" in the removal of blood clots from the vessels of individuals who have experienced a heart attack. Cyclosporin A, another bioactive molecule, is derived from the fungus Trichoderma polysporum and is employed as an immunosuppressive agent in organ transplant patients. Statins, on the other hand, are produced by the yeast Monascus purpureus and have been commercialised as agents to lower blood cholesterol levels. They function by competitively inhibiting the enzyme responsible for cholesterol synthesis. Biofertilisers are organisms that enhance the nutrient quality of the soil and can be derived from bacteria, fungi, and cyanobacteria. Rhizobium bacteria form nodules on the roots of leguminous plants and convert atmospheric nitrogen into organic forms, which serve as nutrients for the plants. Additionally, certain free-living bacteria like Azospirillum and Azotobacter can fix atmospheric nitrogen in the soil, thereby enriching its nitrogen content. Fungi also engage in symbiotic associations with plants, known as mycorrhiza. Many members of the Glomus genus form mycorrhiza, wherein the fungal symbiont absorbs phosphorus from the soil and transfers it to the plant. These associations offer various benefits to the plants, including enhanced resistance to root-borne pathogens, increased tolerance to salinity and drought, and an overall improvement in plant growth and development.

Lactic acid bacteria (LAB) convert milk to curd. They also improve the nutritional quality of curd by increasing:

Answer & explanation+

Correct answer: option 3

The correct answer is Option (3) → Vitamin B12

Lactic acid bacteria (LAB), such as Lactobacillus, grow in milk and turn it into curd. The acids they make coagulate and partly digest the milk proteins. A little curd added to fresh milk works as a starter, because it contains millions of LAB. Besides making curd, the LAB raise the vitamin B12 content, which improves the nutritional quality of curd. In our stomach too, LAB help to check disease-causing microbes.

NCERT Extract:
Microbes in Household Products – “… Micro-organisms such as Lactobacillus and others commonly called lactic acid bacteria (LAB) grow in milk and convert it to curd. During growth, the LAB produce acids that coagulate and partially digest the milk proteins. A small amount of curd added to the fresh milk as inoculum or starter contain millions of LAB, which at suitable temperatures multiply, thus converting milk to curd, which also improves its nutritional quality by increasing vitamin B12.”

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