Autochthonous Acid-Producing Bacteria from Catfish (Clarias sp.) with Antibacterial Activity against Selected Fish Pathogens: A Preliminary Study

In this study, the application of an autochthonous microorganism as probiotic on catfish (Clarias sp.) was scarcely reported. This study aimed to obtain probiotic candidates from the digestive tract (intestinal and gastric) of catfish. A total of nine isolates were successfully isolated from the catfish. Almost all bacterial colonies were morphologically round, had flat edges, were yellow, and produced clear zones as a sign of producing acid during culture. The analysis showed that the three isolates had the best activity in inhibiting fish pathogen isolates. Furthermore, molecular analysis revealed that those three isolates were Bacillus velezensis UB-C1, Bacillus amyloliquifaciens UB-C5, and Bacillus cereus UB-C8. Interestingly, those three bacteria were non-lactic acid bacteria.