Abstract: Cardio-cerebrovascular diseases have seriously threatened human health,and morbidity and mortality from them are the highest among all kinds of diseases. Nattokinase is widely concerned as an ideal naturally functional food for prevention and treatment of thrombosis,thus the research on the scale production of nattokinase is of great significance to promote the development of thrombolytic functional food. Based on the previous optimization study of fermented soybean milk technology and slightly adjusting the factor sequence and factor level,the fermentation conditions were optimized by single factor and orthogonal experiments,while using whole soybean milk as fermentation medium,nattokinase as function evaluation index,and the slag rate and finial pH as auxiliary indexes. Result showed that the optimal fermentation conditions were determined as follows：the fermentation time was 30 h,the liquid volume in flask was 5%,the initial pH was 5.5,and the amount of bacteria was 1.5%. The nattokinase activity was 660 184.14 IU/mL under this condition,which was 8.31 times of that before optimization（79 434.68 IU/mL）and 1.54 times of previous optimized study（429 869.34 IU/mL）. The enzyme production significantly increased by adjusting initial pH and the order of inoculation even with lower amount of inoculation,compared to the optimized process of whole bean milk with inoculation 1.75% . This study confirmed that the cost can be eliminated while the nattokinase production can be improved,which is significant for the large-scale production of nattokinase.

Key words: soymilk, liquid fermentation, nattokinase, optimization