Microbial Cell Factories for Phenylethanoid Glycosides: A Review on Engineering Strategies and Perspectives

Due to the neuroprotective and antioxidant properties, phenylethanoid glycosides (PhGs) are valuable plant-derived compounds. Traditional extraction methods are constrained by low yields and limited resources, prompting the integration of synthetic biology and enzyme engineering technologies for sustainable production. This review summarizes the advances in the microbial synthesis of PhGs, emphasizing the elucidation of biosynthetic pathways, enzyme engineering modifications of glycosyltransferases and acyltransferases, and strategies for optimizing microbial cell factories in Escherichia coli and Saccharomyces cerevisiae. Significant advancements encompass the efficient synthesis of verbascoside and echinacoside in S. cerevisiae, as well as the comprehensive elucidation of the echinacoside biosynthetic pathway in Cistanche spp., including the identification of key steps catalyzed by a rhamnosyltransferase, a CYP450 hydroxylase, and a terminal glucosyltransferase that enable pathway reconstruction in S. cerevisiae. We conduct a systematic analysis of methods to address the biosynthetic bottlenecks via protein engineering, including rational design and directed evolution, as well as the metabolic engineering strategies such as precursor enhancement and cofactor recycling. Additionally, we investigate the synthesis of non-natural PhG analogues and the prospective integration with AI-assisted design, emphasizing the significant potential of microbial systems in overcoming the supply challenges for medicine-food homologous ingredients.