Production of thermostable, Ca+2-independent, maltose producing α-amylase by Streptomyces sp. MSC702 (MTCC 10772) in submerged fermentation using agro-residues as sole carbon source

Abstract

The purpose of this study was to determine the influence of growth conditions and medium composition on the thermostable, Ca+2-independent, maltose producing α-amylase production in submerged fermentation (SmF) by Streptomyces sp. MSC702—a strain newly isolated from mushroom compost. Production of α-amylase enzyme by a Streptomyces strain was detected on semi-synthetic media containing rice bran and wheat bran in a 1:2 ratio as the sole carbon source. The effect on α-amylase production of different medium ingredients and additives, such as NaCl, additional carbon sources, nitrogen sources, metal salts, nucleotides, phytohormones, surfactants and other chemicals, was examined. NaCl played no notable role in the biosynthesis of α-amylase, with the strain being able to grow at 14% (w/v) NaCl with ~76% α-amylase activity. Among the different cations tested, Hg2+ showed no inhibitory effect on α-amylase production. The best combination of physical parameters for the maximum production of α-amylase was a temperature of 50°C, pH 7.0 and an incubation period of 48 h. The best combination of chemical parameters with rice bran 1.0% (w/v) and wheat bran 2.0% (w/v) was dipotassium hydrogen phosphate 0.1% (w/v), magnesium sulfate 0.1% (w/v) with d-inositol (as additional carbon source) 1.0% (w/v), peptone (as nitrogen source) 0.1% (w/v), manganese sulphate (as additional metal ion) 0.05% (w/v) and Tween-80 (as surfactant) 1.0% (v/v). With the application of these culture conditions, α-amylase production increased by ~1.42 fold.