This study aimed to isolate bacterial strains from fermented keluak and evaluate their antibacterial activity against Salmonella typhimurium. Bacterial isolation was performed using the pour-plate technique. The isolates were characterized macroscopically based on colony morphology and microscopically using Gram staining and endospore staining. Physiological characterization was further conducted using catalase and motility tests. Antibacterial activity was evaluated using the agar well diffusion method, in which the wells were filled with cell-free supernatants obtained from the bacterial isolates, distilled water as the negative control, and erythromycin as the positive control. Antibacterial activity was determined by measuring the diameter of the inhibition zones using a vernier caliper. A total of 12 bacterial isolates were obtained, six of which were identified as lactic acid bacteria (LAB). Among the LAB isolates, K21A exhibited the largest inhibition zone (8.85 mm), whereas K32B showed the smallest inhibition zone (1.45 mm). In comparison, the positive control produced an average inhibition zone of 16.25 mm. These findings demonstrate that LAB isolated from fermented keluak produce cell-free supernatants with antibacterial activity against S. typhimurium. Thus, fermented keluak may serve as a potential source of antibacterial LAB with prospective applications in the prevention or management of bacterial gastroenteritis.
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