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Proteases which are ubiquitous in occurrence, being found in all living organisms, and are essential for
cell growth and differentiation. The extracellular proteases are of commercial value and find multiple
applications in various industrial sectors especially in especially in food industry. The present study
describes the screening of protease producer from gastrointestinal tract of Labeo rohita. Among the 7
isolates, PPR7 strain was found to be more suitable for protease enzyme production. The morphological,
cultural, biochemical and molecular characteristics of isolate PPR7 revealed as Bacillus thuringiensis.
The temperature and pH was optimized for the maximum production of this enzyme. The optimum
temperature for the protease production (120 U/ml) was found to be 37 °C while the pH was found to be
optimum at 7.00 for the protease production (100.0 U/ml). Medium optimization suggested that the most
appropriate carbon source was glucose (122.0 U/ml), nitrogen source was glycine (130.4 U/ml) and
NaCl concentration was 2% (85.2 U/ml) for the better protease production.
The present research will be helpful for fish nutritionists to utilize this enzyme producing bacterial
isolates as a probiotic formulations, which is not only a cost-effective aqua feeds but is also especially for
the larval stages when the enzyme system is not efficient.
Keywords: Labeo rohita, Bacillus thuringiensis, Protease production, Media optimization, Isolation and
Characterization.