Antibacterial and Enzymatic Activities of Lactic Acid Bacteria From Fermented Foods

Objectives The present study aimed to explore the microbial diversity—specifically, the diversity of lactic acid bacteria (LAB)—in traditional fermented foods from rural areas of Davangere, Tumakuru, and Chitradurga districts of Karnataka, India. The objectives included isolating and characterising LAB, evaluating their antibacterial activity against common food-borne pathogens, and screening for the production of the industrially relevant enzyme, alkaline protease. Material and Methods Samples were collected from naturally fermented foods and subjected to standard microbial isolation protocols, including serial dilution and plating on MRS agar supplemented with 1% CaCO 3 . Isolates were physiologically characterised, and antibacterial activity was assessed using the agar overlay method against Salmonella enterica serovar Typhimurium (MTCC 3231), Staphylococcus aureus (MTCC 737), Escherichia coli (MTCC 1687), and Listeria monocytes (MTCC 1143). Isolates with promising antibacterial activity were further screened for alkaline protease production under varying conditions of temperature, pH, and nutrient sources. Results A total of 122 isolates were obtained. Among these, isolates GP151, GP338, and GP294 demonstrated significant and broad-spectrum antibacterial activity. Of these, GP338 exhibited optimal alkaline protease production at 37°C, pH 10, with starch and lactose as carbon sources and peptone as the nitrogen source. Conclusion This study highlights the presence and diversity of LAB in traditional fermented foods and their potential antibacterial properties. Furthermore, certain LAB isolates, particularly GP338, show promise for industrial applications due to their ability to produce alkaline protease under optimized conditions. These findings suggest potential roles for such isolates in food safety, preservation, and biotechnology, warranting further investigation.