CHARACTERIZATION OF TWO EXTRACELLULAR PROTEASES FROM Streptomyces

Abstract

Proteases derived from actinomycetes have often been shown to possess many remarkable biological properties. In this study, 24/30 actinomycetes isolated from soils were found to be able to synthesize extracellular proteases. Among those actinomycetes, Streptomyces sp. CNXK72 and Streptomyces sp. CNXK100 exhibited the strongest protease production with the zone of substrate hydrolysis of 27.0±0.8 mm and 23.3±0.5 mm, respectively. The macroscopic and microscopic characteristics together with the phylogenetic analysis of 16S rRNA sequences showed that these two strains are closely related to Streptomyces odorifer (99.65%) and Streptomyces ginkgonis (99.86%), respectively. CNXK72-derived protease is active between 30-80°C, pH range of 4.0-10.0, with maximum activity at 55°C and pH 7.0 in Tris-base buffer. Besides, CNXK100-derived protease has an activity spectrum from 30-100°C, pH 4.0-10.0, and show optimum activity at 75°C, pH 6.0-9.0 in Phosphate and Tris-base buffer, and exhibit 5.6 times more activity than proteases derived from CNXK72. The good substrate hydrolysis at high temperatures and wide pH ranges indicates potential applications in detergent and tanning industries of these two proteases.