Optimal protease production condition for Prevotella ruminicola 23 and characterization of its extracellular crude protease

Abstract

In this study, Prevotella ruminicola 23 (ATCC 19189), a ruminal proteolytic bacterium, was used as protease producer to examine the optimal condition for protease production. The best carbon and nitrogen sources for the maximum growth were glucose with peptone. Both sucrose and glucose could stimulate high protease production. Casein and peptone are better nitrogen sources for protease production than other choice in this study. The best enzyme production condition was 18–20 h incubation which was at late log phase in the broth of 5% glucose or sucrose as carbon source with 0.1% ammonium chloride and 0.2% peptone as nitrogen sources. Most of the protease activity was secreted into broth (65%) and on cell surface (18%). The optimal temperature and pH for protease reaction were 40 °C and pH 6.8, respectively. After incubation for 6 h, the crude extract maintained 50% of original protease activity at 30 and 50 °C, and protease activity was stable between pH 6 and 8. The protease inhibitor test showed that serine, aspartic acid and metallo-protease inhibitors could cause inhibition of proteolysis. Protein feedstuff degradation experiments suggested that protease in crude extract had higher degradation ability on fish meal, whey, and feather meal (2.39, 2.60 and 1.76 μmol amino acid/mg enzyme/h) in comparison to soybean meal and blood meal (1.11 and 1.09 μmol amino acid/mg enzyme/h). The protease in the crude extract should have application potential in term of improving utilization of fish meal and feather meal for monogastric animals.