Abstract

A protease is one of the most used classes of enzymes in various industries. Enzyme production in Indonesia still mainly relies on imports, suggesting that local microbial resources should be investigated. In this study, isolation and optimization of protease-producing bacteria from the intestine of catfish (Clarias sp.) was conducted as a possible local source of industrial enzymes. Eight bacterial isolates were screened on skim milk agar. The most potential isolate was morphologically and molecularly identified as Bacillus sp. Strain UBL. Protease production was investigated by calculating Proteolytic Index (PI) and enzyme activity (U/mL). Optimization was performed using one factor at a time, analysing the influence of initial inoculum concentration (2–6%), pH (6–8), temperature (30–42°C), culture medium, and length of incubation periods. Maximum protease production was achieved at the following conditions: 4% Inoculum (p<0.05), pH 7 (p<0.05), 30°C temperature (p<0.05), under TSB medium, and an incubation period of 16 h (p<0.05). At pooled parameters, the obtained enzyme activity was tabulated at 21.1 ± 0.9 U/mL, having a proteolytic index value of 0.96 ± 0.04 as compared to non-optimized settings with activity being only up to 8.1 ± 4.2 U/mL and PI of just 0.37 ± 0.19, reflecting an augmentation of about 2.6-fold in production of protease released by Bacillus sp. strain UBL under optimized conditions. These results indicate that fish intestinal microbiota represents a potential source of bacterial proteases.