Vol. 9, Issue 12, Part I (2025)

The gut of the table size fish rohu (Labeo rohita) sample was collected from different aquatic environments like community pond, cultured fish pond without probiotic application and cultured fish pond with probiotic application. Then the gut microflora was isolated and pure culture of each isolated one was done aseptically. Their probiotic potentials were analysed by various probiotic potential tests like bio-film formation test by congo red agar method, gastric juice tolerance test, bile juice tolerance test, pH tolerance test, antibiotic susceptibility test. After doing the probiotic potential tests the sample collected from community pond and cultured fish pond without probiotic application showed negative result. But only two isolates, isolate I and II of the gut sample collected from cultured fish pond with probiotc application showed positive results. The two isolates showed dry crystalline black colony formation in congo red agar plate. Both isolates, isolate I & II showed % survivability of 35.38% & 64.70% after 3 hrs inside the gastric juice of pH 2.5. Isolate I showed less tolerance to bile juice than isolate II in bile concentration of 2.5%,5%,7.5%,10% in both 3 hr & 6 hr. During pH tolerance test, both the isolates showed increasing survivability from pH 4 to 7 but after pH 7 the trend started decreasing. In antibiotic susceptibility test, both the isolates were more susceptible to ampicilin and less susceptible to vanomycin. But more antibiotic susceptibilty was shown by isolate I than isolate II. From the above probiotic potential tests it was concluded that isolate II was having more probiotic potential than isolate I. Some biochmeical tests were done to identify the isolates whose results showed that isolate I as Bacillus coagulans & isolate II as Bacillus polymyxa.