Optimization of alkaline protease production by Streptomyces sp. strain isolated from saltpan environment

Abstract

Proteolytic activity of a Streptomyces sp. strain isolated from Ezzemoul saltpans (Algeria) was studied on agar milk at three concentrations. The phenotypic and phylogenetic studies of this strain show that it represents probably new specie. The fermentation is carried out on two different media, prepared at three pH values. The results showed the presence of an alkaline protease with optimal pH and temperature of 8 and 40°C, respectively. The enzyme is stable up to 90°C, having a residual activity of 79% after 90 min. The enzyme production media are optimized according to statistical methods while using two plans of experiences. The first corresponds to the matrixes of Plackett and Burman in N=16 experiences and N-1 factors, twelve are real and three errors. The second is the central composite design of Box and Wilson. The analysis of the results allowed the selection of two factors having a significant effect on the production of the enzyme (fructose and malt extract), then defining theirs optima (7 g/l of fructose and 12 g/l of malt extract).

Keywords: Protease, streptomyces, identification, fermentation, optimization