基于尿苷二磷酸葡萄糖循环再生系统高效转化酪醇合成红景天苷

Efficient synthesis of salidroside from tyrosol based on UDPG recycling system

摘要:

红景天苷是一种在食品、医药等领域应用广泛的功能性成分，其传统生产方法为植物提取，原料成本高昂且提取过程繁琐。本研究通过生物合成法，以酪醇为底物高效生产红景天苷。在利用糖基转移酶实现酪醇糖基化的同时，引入蔗糖合酶构建尿苷二磷酸葡萄糖(uridine diphosphate glucose, UDPG)循环再生系统。通过比较，筛选出糖基转移酶UGT33以及蔗糖合酶AtSUS，构建重组大肠杆菌(Escherichia coli) BL21/pETDuet-AtSUS-UGT33，并针对基因的拷贝数进行了优化，确定糖基转移酶与蔗糖合酶的最优拷贝数比例为3:1。进一步对重组菌株的全细胞催化条件进行优化，在最适反应温度、pH、菌体量、底物浓度、适量金属离子的最优反应条件下，在5 L发酵罐转化24 h，红景天苷最高产量达到8.17 g/L。本研究为利用微生物高效生产红景天苷提供了一定的参考意义。

Abstract:

Salidroside is a functional ingredient with wide applications in food and pharmaceutical fields. It is conventionally produced by extraction from plants, the application of which is limited by the scarcity of raw materials and cumbersome process. This study achieved the efficient production of salidroside by biosynthesis with tyrosol as the substrate. While utilizing glycosyltransferases for tyrosol glycosylation, we introduced sucrose synthase to construct the uridine diphosphate glucose (UDPG) recycling system. The glycosyltransferase UGT33 and sucrose synthase AtSUS were screened out by comparison, and the recombinant strain Escherichia coli BL21/pETDuet-AtSUS-UGT33 was constructed. The copy number of the gene was optimized and the optimal copy number ratio of glycosyltransferase to sucrose synthase was determined to be 3:1. The whole-cell transformation conditions (temperature, pH, inoculum amount, substrate concentration, and concentrations of metal ions) of the recombinant strain were optimized, and the highest yield of salidroside reached 8.17 g/L after fermentation under the optimal conditions in a 5 L fermenter for 24 h. This study provides a reference for the efficient production of salidroside by microorganisms.