纳豆激酶高产菌的快速筛选及其发酵纳豆特性

通过纤溶活性筛选法和纳豆激酶基因筛选法，快速、准确筛选到一株纳豆激酶高产菌株MJ-1，经16S rRNA基因序列分析，该菌株被鉴定为枯草芽孢杆菌。以黄豆为原料进行固体发酵制备纳豆食品，考察了纳豆食品的纳豆激酶活力、抗凝活性和抗氧化活性。在初始含水量60%、发酵温度37 ℃的条件下，纳豆激酶发酵活力在20 h达到最大值（90.18 FU/g，以干质量计），达到了商业化纳豆的酶活力水平。抗凝活性分析显示该菌株可合成抗凝成分，赋予纳豆食品抗凝活性，在提取物质量浓度为3 mg/mL时，抗凝效率达91%。同时，与未发酵黄豆相比，发酵过程显著提高了其抗氧化活性。

Rapid Isolation of a Strain with High Nattokinase Activity and Characterization of As-Fermented Natto Food

Using the screening method based on fibrinolytic activity and nattokinase gene, a strain named MJ-1 with
nattokinase-producing capacity was obtained and identified as Bacillus subtilis by 16S rRNA gene sequence analysis. A
natto functional food was prepared by fermentation of soybean with MJ-1, and its nattokinase activity, and anticoagulant
and antioxidant activity were evaluated. Under the conditions of 60% initial moisture content and 37 ℃, the maximum
nattokinase activity of 90.18 FU/g dry weight was obtained after 20 h fermentation, which reached the activity level of
commercial natto. The strain MJ-1 could secret anticoagulant components, resulting in rich anticoagulant activity in natto
foods, and the anticoagulant activity of natto water extract at 3 mg/mL reached 91%. Moreover, fermentation with MJ-1
improved the antioxidant activity of soybean significantly.