Abstract: Nattokinase is an ideal natural drug for the prevention and treatment of thrombosis. Liquid fermentation can improve the yield of nattokinase. Taking Bacillus subtilis natto as the start culture, soybean milk as the fermentation medium, nattokinase activity as function evaluation index, the slag rate and finial pH as auxiliary indexes, the effects of fermentation time, liquid loading, bacteria loading and initial pH on nattokinase activity were studied by single factor and orthogonal analysis. The optimal fermentation conditions were determined as follows: The fermentation time was 30 h, the liquid volume in flask was 5%, the amount of bacteria was 1.75%, and the initial pH was 5.5. The nattokinase activity was 429 869.34 IU/mL under this condition, which was 5.41 times of that before optimization. It can be seen that the orthogonal test successfully optimized the liquid fermentation process of Bacillus subtilis natto and significantly increased the expression of nattokinase, which laied a theoretical foundation for the development of functional food.

Key words: soybean milk, liquid fermentation, nattokinase, optimization

摘要： 纳豆激酶具多效溶栓作用，是一种理想的预防和治疗血栓的天然药物。液体发酵可提高纳豆激酶产量。以纳豆枯草芽胞杆菌为出发菌株，豆乳为发酵基质，纳豆激酶活力为核心评价指标，出渣率和终点pH为辅助评价指标，通过单因素和多因素统计学分析研究发酵时间、装液量、接菌量和初始pH对纳豆激酶活力的影响，优化发酵条件，以期提升纳豆激酶的表达量。最终确定最优发酵工艺为：摇瓶豆乳的发酵时间30 h，装液量5%，接菌量1.75%，初始pH 5.5。在该发酵条件下，纳豆激酶的活力为429 869.34 IU/mL，是优化前的5.41倍。可见，正交试验成功优化了纳豆枯草芽孢杆菌的液体发酵工艺，显著提升了纳豆激酶的表达量，为功能食品开发奠定了理论基础。

关键词: 豆乳, 液体发酵, 纳豆激酶, 工艺优化