Isolation and Characterization of Extracellular Enzyme Producing Bacilli in the Digestive Tracts of Rohu, Labeo rohita (Hamilton) and Murrel, Channa punctatus (Bloch)

Isolation of some extracellular enzyme producing aerobic bacteria in the digestive tracts of rohu (Labeo rohita, Cyprinidae) and murrel (Channa punctatus, Channidae) was carried out. Gut bacteria were isolated on tryptone soya agar (TSA) plates. The isolated strains were qualitatively screened based on their extracellular protease, amylase and cellulase producing ability using selective media. Among the strains isolated, LrB1 and CpB2 isolated from L. rohita and C. punctatus, respectively, seemed to be the superior strains. The strains were characterized based on morphological, physiological and biochemical characterization and identified as Bacillus subtilis (LrB1) and Bacillus cereus (CpB2). They tolerated a wide range of temperature (15-55C), pH (5-11) and NaCl (1-25%). Biochemical characterization suggests that the isolates are capable of hydrolyzing proteins and carbohydrates indicating their importance in fish nutrition. The information generated from the present investigation could contribute towards the utilization of such autochthonous enzyme-producing bacteria for nutrition in fish with better efficiency.