Optimization of submerged fermentation medium and condition of chickpea natto

In order to increase the protease activity in natto,chickpea natto submerged fermentation was optimized with Bacillus subtilis natto in this research,protease activity was taken as determining index and three most effective factors were screened out by Plackett-Burman method:liquid volume, rotate speed and chickpea powder. Response surface method was used to optimize the fementation medium and condition and quadratic regression model.The quadratic regression model that set up in response surface showed the good regression level, which indicated the effect on the improvement of protease activity was significant(p<0.05). The optimization we got for medium:chickpea powder 5.9%, soya bean meal powder 1.0%, glucose 0.6%,NaCl 0.5%, the best incubation condition:rotate speed 250 r/min, liquid volume 76/500 mL, fermented under the condition of 37℃ and 48 hours. The protease activity reached (3558.0±1.5) U/mL and had increased 42.8% under this condition compared with initial(2491.4±2.8) U/mL,while the dissolved area of nattokinase tested by fibrin plate method had also increased 108.6%. The results showed that the optimized submerged fermentation of chickpea natto could significantly improve the protease activity.