Screening and Characterization of Tyrosinase Producing Bacteria from Sauce Prepared Using Rohu and Sardine by Enzymatic and Fermentative Method

Fish sauce was prepared from Rohu (Labeo rohita) and Sardine (Sardinella longiceps) by enzymatic and fermentative method using papain and Pediococcus pentosaceus FSBP4-40. Total tyrosinase producing bacteria counts of enzymatically and fermentatively produced rohu sauce samples were found to be in the range of 1.70 to 3.65 log cfu/ml and 1.95 to 3.64 log cfu/ml, respectively. The enzyme treated and LAB fermented sardine sauce samples were found to be in the range of 2.00 to 3.28 and 1.78 to 3.63 log cfu/ml during the storage period of 120 days. Over 60 brown to black coloured colonies on tyrosinase screening medium were screened for the Gram's reaction, cell morphology, proteolytic property catalase and oxidase activities. Of these, 5 isolates coded as PTRS-8, PTSS-3, LTRS-11, LTRS-18 and LTSS-5 were characterized by biochemical and molecular methods. The isolate PTRS-8 (Bacillus endophyticus) exhibited excellent antibacterial activity against Listeria monocytogenes Scott A and the isolate PTSS-3 (Bacillus aquimaris) showed higher proteolytic activity. All the isolates were able to produce alkaline phosphatase and naphthol-AS-B1-phosphohydrolase, esterase (C4), esterase lipase (C8) and a-chymotrypsin. The isolate PTSS-3 exhibited excellent leucine arylamidase activity. The melanogenic nature of the isolates is one of the probable properties responsible for the development of color in fish sauce.