Which of the following plays a significant role in our stomach in che…

The correct answer is Option (4) → Lactobacillus

Option (1) Penicillium notatum — Incorrect. This mould produces the antibiotic penicillin, discovered by Alexander Fleming. It is not a microbe that lives in our stomach.

Option (2) Monascus purpureus — Incorrect. This yeast produces statins, which lower blood cholesterol.

Option (3) Trichoderma polysporum — Incorrect. This fungus produces cyclosporin A, an immunosuppressive drug given to organ-transplant patients.

Option (4) Lactobacillus — Correct. Lactobacillus is a lactic acid bacterium (LAB). It turns milk into curd and raises its vitamin B₁₂ content.

NCERT Extract:
Microbes in Household Products – “… You would be surprised to know that we use microbes or products derived from them everyday. A common example is the production of curd from milk. 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. In our stomach too, the LAB play very beneficial role in checking disease-causing microbes.”