Optimization of natto processing conditions based on nattokinase activity

To optimize natto processing condition,nattokinase was applied as the index,being determined by agarose- fibrin plate method.The processing condition by single factor experiment was 15 h of soak time,45 min of cooking time,3% of inoculum size,38 ℃ of fermentation temperature,28 h of fermentation time,and 1 d of postripeness time.The optimal condition by response surface was 15 h of soak time,51 min of cooking time,and37.5 ℃ of fermentation temperature.The highest nattokinase activity was 2493.33 U / g.