Optimization of medium composition for recombinant nattokinase production from Bacillus subtillis by using response surface methodology

Nattokinase is a serine protease with fibrinolytic activity whose clinical efficacy and safety for human by the oral route has been proven. In this study, we optimized the medium components for production of recombinant nattokinase from Bacillus subtillis DB104. Carbon and nitrogen sources from the different materials were selected in order to make the base for screening factors affecting nattokinase activity by Plackett-Burman experiments. Among factors surveyed, soya pepton, MgSO 4 and NaCl were considered significant (p<0.05). These factors were subsequently optimized by using the response surface methodology (RSM). The obtained results showed the appropriate mediumfor the biosynthesis of nattokinase included 10 g/l soypepton, 0.88 g/l MgSO 4 , 5 g/l NaCl. After 16 hrs of fermentation, nattokinase activity reached the highest level of 152 FU/ml, 1.8 times higher than that in the pre-optimized one (83 FU/ml).