ABSTRACT
The aim of this study was to use agro-industrial residues for the production of a halotolerant keratinolytic- protease by Actinobacterium sp. in solid-state fermentation. Among various agro-industrial residues that were evaluated, apple pomace supported maximum protease production (8400 U/g material). The optimum conditions required for enzyme production were a fermentation period of 72 h, 10% (w/v) NaCl, pH 7.0, 120% (v/w) moisture and 10% (v/w) inoculum. The enzyme exhibited activity to a range of pH (7.0-9.0) and temperature (30-45°C), with optima at 8.0 and 40 °C, respectively. Most of the divalent ions tested stimulated the protease activity and Ca2+ ion was required for its activity and stability. The enzyme was widely active at the range of NaCl concentration (5%-15%, w/v) and effectively degraded chicken feather. This protease could be useful in fish sauce fermentation and also in feed industry.