Data_Sheet_1_Identification of an Invertase With High Specific Activity for Raffinose Hydrolysis and Its Application in Soymilk Treatment.docx

The hydrolyzation of raffinose into melibiose by using invertases under mild conditions improves the nutritional value of soybean products. However, this strategy has received little attention because a suitable invertase remains lacking. In this study, a novel invertase named InvDz13 was screened and purified from Microbacterium trichothecenolyticum and characterized. InvDz13 was one of the invertases with the highest specific activity toward raffinose. Specifically, it had a specific activity of 229 U/mg toward raffinose at pH 6.5 and 35°C. InvDz13 retained more than 80% of its maximum activity at pH 5.5–7.5 and 25–40°C and was resistant to or stimulated by most cations that presented in soymilk. In soymilk treated with InvDz13 under mild conditions, melibiose concentration increased from 3.1 ± 0.2 to 6.1 ± 0.1 mM due to raffinose hydrolyzation by InvDz13. Furthermore, the prebiotic property of InvDz13-treated soymilk was investigated via in vitro fermentation by human gut microbiota. Results showed that InvDz13 treatment increased the proportion of the beneficial bacteria Bifidobacterium and Lactobacillus by 1.6- and 3.7-fold, respectively. By contrast, the populations of Escherichia and Collinsella decreased by 1.8- and 11.7-fold, respectively. Thus, our results proved that the enzymatic hydrolysis of raffinose in soymilk with InvDz13 was practicable and might be an alternative approach to improving the nutritional value of soymilk.

采用温和条件下的果糖酶对 raffinose 进行水解生成麦芽糖，能显著提升大豆制品的营养价值。然而，由于尚未找到合适的果糖酶，此策略鲜受关注。在本研究中，从 Microbacterium trichothecenolyticum 中筛选并纯化了一种名为 InvDz13 的新型果糖酶，并对其进行了特性描述。InvDz13 是对 raffinose 具有最高专一活性的果糖酶之一。具体而言，其在 pH 6.5 和 35°C 条件下对 raffinose 的专一活性为 229 U/mg。InvDz13 在 pH 5.5–7.5 和 25–40°C 条件下仍保持超过 80% 的最大活性，并对大豆乳中存在的多数阳离子具有耐受性或刺激作用。在温和条件下使用 InvDz13 处理的大豆乳中，由于 raffinose 的水解，麦芽糖浓度从 3.1 ± 0.2 mM 增加至 6.1 ± 0.1 mM。此外，通过人体肠道微生物群的体外发酵实验，研究了 InvDz13 处理大豆乳的益生元特性。结果显示，InvDz13 处理使得有益细菌双歧杆菌和乳杆菌的比例分别增加了 1.6 和 3.7 倍。相比之下，大肠杆菌和柯林斯菌的数量分别减少了 1.8 和 11.7 倍。因此，我们的研究结果证实，使用 InvDz13 在大豆乳中进行的 raffinose 酶解是可行的，并可能成为提升大豆乳营养价值的一种替代策略。