A. YUNIARTI, MAFTUCH, SOEMARNO AND AULANNI, A.M.
Abstract
This study aimed to screen several Bacillus strains as a potential candidate of probiotic for use in shrimp culture. The in-vitro assessment was conducted based on various selective criteria, i.e. production of antimicrobial metabolites, AHL degrading ability, Rank Index, and production of extracellular enzyme. Using morphological, biochemical and molecular study, the isolate of SB1, SB2, SB3 and SB4 were confirmed close to B. thuringiensis, B. cereus, B. subtilis and Bacillus sp., respectively. All Bacillus isolates produced antimicrobial metabolite against three pathogens tested. Furthermore, SB3 had the greatest ability in inhibiting pathogens with an average inhibitory zone of 21.11mm. Based on their growth profile, Rank Index of SB3 was the highest (8.35) compared with others. This means that SB3 had a better opportunity to outcompete other bacteria include pathogens. Concerning enzymatic contribution which could beneficial for host, SB1 and SB3 had better capacities of protease, amilase and lipase production. All Bacillus strains in this study were reported to have an ability to degrade QS signal AHL. The highest of AHL degradation rate was found in SB2 and SB3 (0,896 mg L-1 h-1). Taking into account all criteria together, SB3 which was identified closely resemble to B. Subtilis presented the most potential probiotic for shrimp culture.