MP Board · Class 12 · Biology · Microbes in Human WelfareExplain the role of Lactic Acid Bacteria (LAB) in improving the nutritional quality of milk and in human digestion.

Lactic Acid Bacteria (LAB), such as Lactobacillus species, play an indispensable role in transforming milk into curd and significantly enhancing its nutritional profile. When a small amount of curd containing LAB is added to fresh milk as an inoculum or starter, these bacteria multiply at suitable temperatures and produce organic acids, primarily lactic acid. This acid causes the coagulation and partial digestion of milk protein (casein), turning the liquid milk into semi-solid curd. \nFrom a nutritional perspective, curd is often considered superior to milk because the proliferation of LAB significantly increases the concentration of Vitamin B12, along with other B-complex vitamins, which are crucial for maintaining healthy nerve cells and red blood cells. Furthermore, LAB acts upon the lactose sugar present in milk, breaking it down into simpler forms, which makes curd much easier to digest for individuals who are lactose intolerant. \nIn the human stomach and gastrointestinal tract, LAB functions as a vital component of the natural gut microbiota. They establish a protective barrier along the intestinal lining, which competitively inhibits the growth, colonization, and proliferation of harmful pathogenic bacteria and other disease-causing microbes. By maintaining a balanced and healthy intestinal microflora, LAB enhances overall host immunity, promotes efficient nutrient absorption, and aids in regular gastrointestinal motility, thereby preventing various common digestive disorders and ensuring optimal human health.