Which of the following bacteria is responsible for curdling?

Correct option is C

Ans. (c) Lactobacillus acidophilus
Sol. Lactobacillus acidophilus is responsible for the curdling of milk by fermenting lactose into lactic acid, which lowers the pH and causes milk proteins (mainly casein) to coagulate and form curd. This process is essential in dairy fermentation, including yogurt and curd production.
Explanation of each option:
· (a) Lactic acid bacteria – Incorrect, as this is a general term that includes many species, but the specific bacteria responsible for curd formation is Lactobacillus acidophilus.
· (b) Lactobacillus aureus – Incorrect, as no such bacterial species is responsible for curdling.
· (c) Lactobacillus acidophilus – Correct answer. This bacterium ferments lactose, leading to curd formation.
· (d) Bacillus radicicola – Incorrect, as it is a nitrogen-fixing bacteria found in soil, not involved in dairy fermentation.