IN-VITRO ASSESSMENT AND COMPARATIVE ANALYSIS OF PROBIOTIC BACTERIA FROM DAIRY SOURCES WITH EMPHASIS ON BIOCHEMICAL AND CHEMICAL PROPERTIES

Probiotics are beneficial microorganisms that are crucial for maintaining gastrointestinal balance and defending against harmful infections. This study focused on isolating, characterizing, and comparing probiotic bacteria from various dairy sources, such as raw milk and fermented products, with a particular focus on their biochemical characteristics and functional capabilities. Isolation on de Man, Rogosa, and Sharpe (MRS) agar identified Lactobacillus spp. as the main isolates, along with Bacillus coagulans found in goat milk samples. The isolates demonstrated significant antimicrobial properties against enteric pathogens, with the most substantial inhibition observed against Salmonella spp. (16 mm). Biochemical assessments indicated considerable organic acid production, as shown by a pH drop to 3.8 and a lactic acid concentration of 2.2 mg/ml. Protein analysis revealed significant bacteriocin production (150 µg/ml), further validating their antagonistic properties. Moreover, the isolates displayed strong resilience to simulated gastrointestinal conditions, including acidic pH (2–5) and bile salt concentrations (0.5–2%), indicating their ability to survive and maintain functionality within the host environment. Fourier Transform Infrared (FTIR) spectroscopy validated the existence of functional groups linked to organic acids and protein compounds. Comparative analysis showed that isolates derived from fermented dairy products, especially curd and yogurt, exhibited enhanced probiotic traits, likely due to increased metabolite production during fermentation. In summary, dairy-derived probiotic isolates exhibit strong antimicrobial activity, favourable biochemical properties, and high stress tolerance, underscoring their potential use in functional foods, nutraceuticals, and therapeutic applications.