Optimization and Functional Properties of a Protease from a Fish Gut Isolate Pseudomonas sp. PD14 Grown on Fish Processing Wastes Substrate

Abstract

Extracellular protease production from Pseudomonas sp. PD14 isolated from the gut of rabbitfish, Siganus guttatus, was investigated using fish processing wastes as nitrogen source. Three types of fish processing by-products – namely, heads, bones, and viscera – from yellowstripe scad (Selaroides sp.) and Japanese halfbeak (Hyporhampus sajori), as well as trimmings and viscera from squid (Loligo sp.) were used. Among the fish waste preparations tested, Japanese halfbeak viscera (HV) flour (1.0%) supported the maximum protease production of 365.0 U/mg protein. Effects of media components on protease production in the optimized concentration of HV flour revealed that the protease enzyme can be optimally produced using maltose (0.50%) as a carbon source, at pH 8.0, and incubated for 48 h at 40 °C. Partial characterization of the crude enzyme supernatant showed that the optimum pH and temperature were 8.0 and 50 °C, respectively. Furthermore, the crude protease exhibited thermostability retaining 50% activity at 60 °C and fairly stable up to pH 11.0. Considering the high costs of industrial enzyme production, the use of fish processing wastes for protease production offers a promising future for enzyme biotechnology.