Production and Optimization of Alkaline Protease in Submerged Fermentation by Streptomyces rochei NRC 24

THE PURPOSE of the present research was to study the.production of extracellular alkaline protease by a local isolate, Streptomyces rochei NRC 24, under submerged fermentation (SF) conditions. The isolate exhibited maximum enzyme production with fermentation medium composed of peptone, glucose, K2HPO4, MgSO4.7H2O, NaCl, and CaCl2. The studies on environmental parameters revealed that maximum level of alkaline protease production (220.92 U/ml) was achieved during stationary phase of S. rochei NRC 24 with optimum initial pH 9, inoculum size of 2% from stock spore suspension (5.6 x 106 spores/ml), and with a culture volume of 75 ml in 250 ml Erlenmeyer flasks under shaking conditions of 200 rpm. Of different nitrogen sources, casein and peptone with 0.4% of each proved to achieve the maximum level of enzyme production. Screening experiments on medium components showed that the presence of peptone, glucose, MgSO4.7H2O, NaCl, and CaCl2 was essential for alkaline protease production. The absence of K2HPO4 from the medium did not totally influence the enzyme production.
Based on these results, De Meo's fractional factorial design was applied to find out the optimal conditions for maximal alkaline protease production. Optimization of the medium was carried out in three steps and Streptomyces rochei NRC 24 grew in the optimized medium producing 555.61 U/ ml compared to the growth of the strain on the basal medium before optimization (224 U/ ml).