变形链球菌来源的右旋糖酐酶的克隆表达及酶学性质研究  

Cloning,expression and enzymatic properties of dextranase from Streptococcus mutans

作　　者：汝伟娟 夏冰冰 杨静文 张洪斌 胡雪芹 RU Weijuan;XIA Bingbing;YANG Jingwen;ZHANG Hongbin;HU Xueqin(School of Food and Bioengineering,Hefei University of Technology,Hefei 230000)

机构地区：[1]合肥工业大学食品与生物工程学院,合肥230000

出　　处：《中国食品添加剂》2023年第1期92-100,共9页China Food Additives

基　　金：安徽省自然科学基金(2108085MC120)。

摘　　要：右旋糖酐酶是一种广泛应用于食品、医药、化工等领域的糖酐水解酶。变形链球菌来源的右旋糖酐酶具有发酵周期短,水解效率高等特点。本文成功克隆了来源于变形链球菌的右旋糖酐酶(Smdex)基因,并导入E.coli BL21(DE3)诱导表达Smdex。研究表明,Smdex的最适温度为40℃,该温度下t_(1/2)为196 min,最适pH为5.5,pH=4.5~10可保持80%的酶活,具有良好的热稳定性和pH稳定性。以右旋糖酐T70为底物时,该酶的K_(m)=3.6 mmol/L,k_(cat)=140 s^(-1),可将右旋糖酐T70降解为低聚异麦芽糖(DP=3~10),表明该酶可应用于低聚异麦芽糖的高效制备。Smdex可抑制大肠杆菌、金黄色葡萄球菌的生长,并对内皮细胞、T细胞无毒害作用,初步表明该酶有潜力作为安全的生物防腐剂,水解产物也可作为功能性的益生元。Dextranase is an anhydroglucose hydrolase widely used in food,medicine,chemical industry and other fields. Dextranase derived from Streptococcus mutans has the characteristics of short fermentation period and high hydrolysis efficiency. In this study,the dextranase(Smdex) gene from Streptococcus mutans was successfully cloned. It was transformed into E.coli BL21(DE3) to induce the expression of Smdex. This study showed that the optimum temperature of Smdex was 40 ℃. At 40 ℃,t1/2was 196 min. The optimum pH of Smdex was 5.5,it could maintain 80% of the enzyme activity at pH 4.5~10. The Smdex had good thermal stability and pH stability. When dextran T70 was used as substrate,the Kmof the enzyme was 3.6 mmol/L and kcatwas 140 s^(-1). Dextran T70 could be degraded to isomalto oligosaccharides with DP of 3~10,indicating that the enzyme could be used in preparation of isomalto oligosaccharides efficiently. In addition,Smdex was able to inhibit the growth of Escherichia coli and Staphylococcus aureus. MTT assay showed that Smdex had no toxic effect on epithelial cells and T cells. The preliminary results showed that Smdex had the potential as a safe biological preservative,its hydrolyzate could also be used as a functional prebiotic.

关 键 词：变形链球菌 右旋糖酐酶 酶学性质 低聚异麦芽糖 生物防腐剂 

分 类 号：Q556[生物学—生物化学] Q789[轻工技术与工程—食品科学] TS202.3[轻工技术与工程—食品科学与工程]