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

Salidroside is a high-value plant-derived glycoside with diverse biological activities, but the main industrial salidroside production method, extraction from <i>Rhodiola</i> plants, is insufficient to meet the growing market demand. The biosynthetic route via microbial fermentation is a sustainable and eco-friendly alternative method. <i>De novo</i> synthesis of the precursor tyrosol was established by introducing the <i>ARO10</i> and <i>ADH6</i> genes. Systematic metabolic engineering resulted in 3.0 g/L tyrosol, but accumulated tyrosol inhibited cell growth. Adaptive evolution produced an evolved strain with a 10.0% higher OD₆₀₀ and a 3.3 g/L tyrosol titer. Introducing glucosyltransferase <i>At</i>UGT85A1, and overexpressing phosphoglucose mutase pgm and UDP-glucose pyrophosphorylase galU, achieved <i>de novo</i> synthesis of salidroside. Furthermore, <i>At</i>UGT85A1 was semirationally engineered, resulting in the A21G mutation, which enhanced salidroside production by 31.2%. The optimally engineered strain produced 16.8 g/L salidroside with 0.4 g/(L h) productivity in a 5 L bioreactor. This study laid a foundation for future industrial production of salidroside and provided important guidance for efficient biosynthesis of other tyrosol derivatives.