Abstract: 105 strains of lactic acid bacteria were isolated and identified from dairy products and sour cabbage soup in Bayanhaote fo Inner Mongolia,and a strain producing thermoduric proteinase,named Enterococcus faecium,was screened from the lactic acid bacteria by detecting hydrolysis circle of proteinase and its activity. The experimental results revealed that the optimal conditions for producing thermoduric proteinase are as follows: glucose as carbon and peptone plus beef extract plus yeast powder as nitrogen sources,carbon-nitrogen ratio 0.8; inoculum size 4%,pH 7.0,fermentation temperature 45 ℃ and fermentation time 30 h. Under these conditions,the yield of thermoduric proteinase is 13.13 U/ml. It was found that K2HPO4 and MgSO4 can promote the production of thermoduric proteinase. The activity of this enzyme is the highest at pH 7 and 50 ℃. Based on the above results,the strain is promising in producing thermophilic proteinase.

Key words: lactic acid bacteria, thermoduric proteinase, proteinase activity