Abstract: Strains capable of secreting extracellular elastase were isolated from the soil of the river. Strain No.B1 with the highest- yield elastase was identified as Bacillus subtilis. The enzyme activity was originally 74.25U/ml. After the physical mutation the enzyme activity of strain B9 becomes 120.00U/ml, enhanced 1.62 times higher than the original strains.Simultaneously the optimum conditions of the enzyme production were studied. The most suitable carbon source is sucrose, and nitrogen sources is casein. The orthogonal test was carried on to have discovered that the nitrogen source affected the enzyme activity highly. When the sucrose to used amounts 4% with the casein 3%, and the corn steep liqid 0.1%, the elastase production is the highest. While the optimal fermentation initial pH is pH8.0, 300ml flask ventilation 40ml and vaccination quantity 3%. After the fermentation conditions being optimized, the strain B9, enzyme activity is 311.54U/ml, enhanced 2.59 times higher, than the former domestic report enzyme activity.

Key words: elastase, Bacillus sp, production condition