Characterization and Identification of Enzyme‐producing Bacteria Isolated from the Digestive Tract of Bata, Labeo bata

Isolation and enumeration of aerobic bacterial flora in the foregut and hindgut regions of the gastrointestinal tract of bata, Labeo bata , were carried out on selected nutrient media following the enrichment culture technique. Four bacterial isolates were qualitatively screened on the basis of their extracellular enzyme‐producing ability. The selected strains were further quantitatively assayed for amylase, cellulase, and protease activities. Amylolytic strains were present in higher densities in the foregut region, whereas the cellulolytic and proteolytic populations exhibited maximum densities in the hindgut region. Peak amylase, cellulase, and protease activities were exhibited by bacterial strains BF2 and BH4, isolated from the foregut and hindgut regions, respectively. Both the strains are Gram‐positive rods, motile, and capable of forming endospores. They can tolerate a wide range of temperatures (25–42 C and 25–55 C in cases of BF2 and BH4, respectively) and pH (5–11). On the basis of phenotypic characteristics and 16S rDNA sequence analysis, the strains were identified as Bacillus licheniformis (BF2, GenBank Accession Number: EF635428) and Bacillus subtilis (BH4, GenBank Accession Number: EF032683). The study provides scope for further research on the use of the enzyme‐producing fish gut bacteria in aquafeeds, especially for the larval stages.