The bacterium Lactobacillus plays a primary role in which one of the following processes?

Correct Option

The correct option is

Coagulation of milk into curd

Explanation

Lactobacillus is a genus of bacteria belonging to the group known as Lactic Acid Bacteria (LAB). These microorganisms are essential in fermentation processes, particularly in the conversion of milk into curd through the production of lactic acid.

Option Analysis

• Alcoholic fermentation is Incorrect. Alcoholic fermentation is primarily driven by yeasts, specifically Saccharomyces cerevisiae (Brewer’s yeast). This process involves the conversion of sugars into ethanol and carbon dioxide, used in brewing and baking.
• Coagulation of milk into curd is Correct. Lactobacillus multiplies in milk and converts lactose sugar into lactic acid. The acid produced coagulates and partially digests the milk protein (casein), transforming the liquid milk into semi-solid curd. This process also enhances the nutritional value by increasing Vitamin B₁₂ content.
• Biological nitrogen fixation is Incorrect. Biological nitrogen fixation is the conversion of atmospheric nitrogen into ammonia, a form usable by plants. This role is performed by specific bacteria such as Rhizobium (symbiotic) and Azotobacter (free-living), not by LAB.
• Biodegradation of polymers is Incorrect. Biodegradation of polymers refers to the breakdown of synthetic or natural polymers by various microbes (e.g., certain species of Pseudomonas or fungi). While some bacteria degrade polymers, it is not the primary characteristic or industrial application of Lactobacillus.

Key Takeaway: Lactobacillus facilitates the souring and coagulation of milk by converting lactose into lactic acid, which precipitates the milk protein casein to form curd.