Production and biochemical characterization of an alkaline protease from Aspergillus oryzae CH93

In this study, Aspergillus oryzae CH93 was isolated from soil sample and examined using molecular analysis. Following culture of A. oryzae CH93 under optimal enzyme production, a 47.5kDa extracellular protease was purified using ammonium sulfate precipitation and Q-Sepharose chromatography. The optimal pH 8 and temperature of 50°C obtained for the isolated protease. Sodium dodecyl sulfate (SDS), cetyltrimethyl ammonium bromide (CTAB), H₂O₂ decreased activity, while Triton X-100 and phenylmethanesulfonyl fluoride (PMSF) had no inhibitory effect on the enzyme activity; meanwhile, 2-mercaptoethanol and ethylenediaminetetraacetic acid (EDTA) declined the protease activity. Isoamyl alcohol and acetone (30%) enhanced activity whereas 2-propanol, isopropanol and dimethyl sulfoxide (DMSO) (30%) reduced protease activity. The enzyme exhibited a half-life of 100min at its optimum temperature. Among five substrates of bovine serum albumin (BSA), N-acetyl-l-tyrosine ethyl ester monohydrate (ATEE), casein, azocasein and gelatin results showed that casein is the best substrate with V_max of 0.1411±0.004μg/min and K_m of 2.432±0.266μg/ml. In conclusion, the extracted protease from A. oryzae CH93 as a fungal source possessed biochemical features which could be useful in some application usages.