本文以少孢根霉（Rhizopus oligosporus）为对照研究了豆豉中的一个分离菌株米根霉（Rhizopus oryzae）产生酸性蛋白酶的条件及所产蛋白酶的性质，结果表明这个菌株的产酶条件和蛋白酶的性质与少孢根霉相比有相似性但也存在一些差异：米根霉在水分含量57%~59%、pH 2.5~3.0的酸性介质中、28~31 ℃下培养36 h时产酸性蛋白酶能力最强，所分泌的蛋白酶系在pH 4.0和pH 6.0附近有最强的催化活性，在pH 3.0~6.0的范围内有较好的稳定性，催化反应的最适作用温度为50 ℃，它的温度稳定性很差，在50 ℃保温30 min已完全失活；少孢根霉在水分含量52%~55%、pH 2.5~3.0的酸性介质中、31 ℃下培养48 h时产酸性蛋白酶能力最强，在35 ℃条件下培养36 h也能产生较高的酶活力，少孢根霉分泌的蛋白酶系在pH 3.0和pH 6.0附近有最强的催化活性，在pH 4.0～6.0范围内很稳定，催化反应的最适作用温度可达55~60 ℃，但它的温度稳定性较差，在50 ℃保温30 min，酶活力损失达到90%，保温120 min酶几乎完全失活。

The culture condition for maximum yield of an acid protease from Rhizopus oryzae and Rhizopus oligosporus and the properties of the protease were studied in this research. The results showed that the optimum conditions for maximum production of acid protease from Rhizopus oryzae grown on wheat bran were water content of 57%~59%, pH of 2.5~3.0, fermentation temperature of 28~31 ℃ and time of 36 h. The best pH value and temperature of the achieved protease were 4.0~6.0 and 50 ℃, respectively. The protease showed high pH stability within 3.0~6.0 and poor thermo-stability, which might lose its activity when incubated at 50 ℃ for 30 min. The optimum conditions for maximum production of acid protease from Rhizopus oligosporus grown on wheat bran were water content of 52%~55%, pH value of 2.5~3.0, fermentation temperature of 31 ℃ for 48 h or fermentation temperature of 35 ℃ for 36 h. The highest activity of the protease from Rhizopus oligosporus was obtained pH3.0 or pH6.0, and temperature of 55~60 ℃. It showed high pH stability at 4.0~6.0, but lower thermal stability at 50 ℃. It was found that nearly 90% of the protease activity was lost when incubated at 50 ℃ for 30 min.