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 47.5 kDa 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 100 min 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 Vmax of 0.1411 ± 0.004 μg/min and Km of 2.432 ± 0.266 μg/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.

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