Revisiting Substrate Specificity Concept in Microbial Screening Methodologies for Fish Waste Management

Microbial and enzymatic processing is an attractive area for production of valuable byproducts from fish waste. Functional screening methodologies for the purpose are still based on activities in non-specific substrates, and concept of substrate specificity is not yet validated. Therefore, reliability of using non-specific substrate for the purpose was checked. Results revealed the existence of a limited number of mutually inclusive positive isolates in non-specific and specific substrate based assays (13% for fish proteolysis and 22% for fish lipolysis), with no significant positive correlations (P>0.05). Further, using non-specific substrates in screening assays missed 57.1% and 53.33% of fish proteolytic and fish lipolytic microbes respectively, signifying the use of same substrates. Beyond methodological perspectives, the paper forms the first report on fish proteolytic activity of Bacillus tropicus, Bacillus vallismortis, Paenibacillus alvei, Staphylococcus epidermidis and Staphylococcus hominis. Similarly, fish oil hydrolyzing capacities of B. tropicus, Cronobacter sakazakii, P. alvei, Paenibacillus pinisoli, Pantoea stewartii, S. hominis and Staphylococcus caprae are recorded for the first time. Further, the paper points out 6 and 3 potential microbial species producing > 1 protease units/ml and >1 enzymatic index for fish proteolytic and lipolytic activities, without any optimization, warranting future use in fish waste management