Isolation and Identification of Protease-Producing Pseudomonas sp. PD14 in the Gut of Rabbitfish Siganus guttatus (Bloch 1787)

Abstract

Bacterial enzymes associated with the gut of fish are known to aid in digestion and nutrition of the host. Isolation, identification and characterisation of protease-producing bacteria from the gut of rabbitfish Siganus guttatus (Bloch 1787) were carried out in the present study. Protease-producing bacteria were isolated in peptone gelatin agar (PGA) plates and the isolated strains were qualitatively and quantitatively screened for enzyme production. Highest protease activity, 25.32±1.06 U.mg-1 protein, was observed in bacterial isolate PD14. Biochemical and molecular analysis revealed that the isolate is 99% homologous to Pseudomonas sp. The 16S rRNA gene sequence of the isolate was deposited in GenBank with accession number KR779515. Qualitative tests on enzyme production through measurement of the zone of hydrolysis further suggest that optimum protease production was 36 h at 40 oC, pH 7-8 in a peptone gelatin agar with 2% NaCl. The data gathered from this study could contribute to the utilisation of such bacteria in fish nutrition or other biotechnological applications.