Multi-strategy integration improves 28-O-glucosylation of asiatic acid into asiatic acid monoglucoside

Abstract

Asiaticoside is a typical triterpene saponin with many important bioactivities that has been widely applied in food and cosmetics fields. Asiaticoside is currently extracted from Centella asiatica but this production method cannot meet market demand. Omics and synthetic biology analyses gradually clarified the endogenous synthesis pathway of asiaticoside in C. asiatica, and production via a heterologous synthetic microbial cell factory has been explored. De novo asiaticoside biosynthesis was achieved and glycosylation was found to be a key limiting factor. Herein, we enhance the efficiency of 28-O-glucosylation of asiatic acid into asiatic acid monoglycoside. By comparing different plant-derived UDP-glycosyltransferases, optimising promoters and co-expressing solubilising tags, and employing rational design, the efficiency of this step was enhanced 3.63-fold, reaching 67.6%. By further evaluating the influence on the muti-enzymatic cascade for asiaticoside synthesis from asiatic acid, asiaticoside production was increased 3.37-fold. The strategies provide references for UDP-glycosyltransferase expression and glycosylation of natural products. This obtained result presents an effective approach to enhance glucosylation of asiatic acid, and provides a reference for glycosylation modification of other triterpenoids.