Engineering Escherichia coli for Efficient <i>De Novo</i> Synthesis of Salidroside

Salidroside is a high-value plant-derived glycoside with\ndiverse\nbiological activities, but the main industrial salidroside production\nmethod, extraction from <i>Rhodiola</i> plants, is insufficient\nto meet the growing market demand. The biosynthetic route via microbial\nfermentation is a sustainable and eco-friendly alternative method. <i>De novo</i> synthesis of the precursor tyrosol was established\nby introducing the <i>ARO10</i> and <i>ADH6</i> genes. Systematic metabolic engineering resulted in 3.0 g/L tyrosol,\nbut accumulated tyrosol inhibited cell growth. Adaptive evolution\nproduced an evolved strain with a 10.0% higher OD<sub>600</sub> and\na 3.3 g/L tyrosol titer. Introducing glucosyltransferase <i>At</i>UGT85A1, and overexpressing phosphoglucose mutase pgm and UDP-glucose\npyrophosphorylase galU, achieved <i>de novo</i> synthesis\nof salidroside. Furthermore, <i>At</i>UGT85A1 was semirationally\nengineered, resulting in the A21G mutation, which enhanced salidroside\nproduction by 31.2%. The optimally engineered strain produced 16.8\ng/L salidroside with 0.4 g/(L h) productivity in a 5 L bioreactor.\nThis study laid a foundation for future industrial production of salidroside\nand provided important guidance for efficient biosynthesis of other\ntyrosol derivatives.