Read the Passage carefully and answer the questions.

Microbes in human welfare

Microbes are a very important component of life on earth. we use microbes and microbially derived products almost every day, like LAB to make curd, yeast to make bread, adding flavor and texture to cheese, producing antibiotics etc. The addition of LAB, improves the milk quality by increasing vit. B12. Cheese is one of the oldest food items in which microbes are used. For example, large holes in Swiss cheese are due to CO2 produced by the bacterium Propionibacterium sharmanii. The BOD test measures the rate of uptake of oxygen by microorganisms in a sample of water and thus, indirectly, BOD is a measure of the organic matter present in the water. The greater the BOD of waste water, the more is its polluting potential. In anaerobic sludge digesters, bacteria produce a mixture of gases like methane, hydrogen sulphide and carbon dioxide. These gases form biogas and can be used as a source of energy. Biofertilisers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilisers are bacteria, fungi and cyanobacteria. You have studied about the nodules on the roots of leguminous plants formed by the symbiotic association of Rhizobium. These bacteria fix atmospheric nitrogen into organic forms, which is used by the plant as a nutrient. Other bacteria can fix atmospheric nitrogen while free-living in the soil (examples Azospirillum and Azotobacter).

Which statement is true about LAB?

Addition of LAB in milk improves the nutritional quality by increasing vitamin $B_{12}$.

The correct answer is Option (2) → Addition of LAB in milk improves the nutritional quality by increasing vitamin $B_{12}$. 

In the process of preparing milk products, a starter inoculum containing millions of Lactic Acid Bacteria (LAB), such as Lactobacillus, is added to skimmed or cream milk at temperatures around 40⁰C or below. These LAB convert the lactose sugar in milk into lactic acid, causing the coagulation of milk protein casein and transforming the milk into curd. Beyond this curdling process, LAB enhance the nutritional quality of curd by increasing the presence of vitamin B₁₂.

Moreover, the LAB present in curd play a vital role in inhibiting the growth of disease-causing microbes in the stomach and other parts of the alimentary canal. The beneficial functions of LAB extend beyond curdling milk, encompassing nutritional enhancement and protective measures against harmful microorganisms.