Clarification and reprogramming of glucose and xylose metabolism in Sphingomonas sanxanigenens for efficient sanxan biosynthesis.

Currently, the production of high-value chemicals from natural lignocellulose is of great significance for a circular economy. In this study, a robust platform was developed based on Sphingomonas sanxanigenens NXdP, which co-utilizes glucose and xylose to synthesize polysaccharide sanxan, for efficient bioconversion of lignocellulose-derived sugars. Sanxan is a promising high-value product due to its high viscosity at low concentrations, excellent acid-gelling capabilities, and unique rheological characteristics. Through a cell growth-based screening strategy and gene manipulation, a key transporter (0233) required for the uptake of both glucose and xylose was identified, clarifying the co-utilization mechanism. Additionally, the metabolic pathways of glucose and xylose were individually blocked to assess their contributions and activities. Furthermore, the metabolic network of strain NXdP was reprogrammed via a "flux-redirection" strategy to develop a potential microbial host with improved sanxan production on mixed sugars. The final engineered strain S09 achieved a sanxan titer of 20.25 ± 0.78 g/kg under mixed-sugar fermentation, representing a 13.51% ± 4.38% increase compared with the original strain NXdP. The mechanism underlying this enhanced production was revealed by central carbon metabolism (CCM) analysis. Overall, this study provides insights into the efficient conversion of lignocellulose-derived sugars and offers genetic components for the green production of other high-value-added products.