Producing D‑Ribose from D‑Xylose\nby Demonstrating a Pentose Izumoring Route

D-Ribose plays fundamental\nroles in all living organisms\nand has been applied in food, cosmetics, health care, and pharmaceutical\nsectors. At present, D-ribose is predominantly produced by\nmicrobial fermentation based on the pentose phosphate pathway (PPP).\nHowever, this method suffers from a long synthetic pathway, severe\ngrowth defect of the host cell, and carbon catabolite repression (CCR).\nAccording to the Izumoring strategy, D-ribose can be produced\nfrom D-xylose through only three steps. Being not involved\nin the growth defect or CCR, this shortcut route is promising to produce D-ribose efficiently. However, this route has never been demonstrated\nin engineering practice, which hinders its application. In this study,\nwe stepwise demonstrated this route and screened out higher active\nenzymes for each step. The first D-ribose production from D-xylose through the Izumoring route was achieved. By stepwise\nenzyme dosage tuning and process optimization, 6.87 g/L D-ribose was produced from 40 g/L D-xylose. Feeding D-xylose further improved the D-ribose titer to 9.55 g/L.\nFinally, we tested the coproduction of D-ribose and D-allose from corn stalk hydrolysate using the route engineered herein.\nIn conclusion, this study demonstrated a pentose Izumoring route,\ncomplemented the engineering practices of the Izumoring strategy,\npaved the way to produce D-ribose from D-xylose,\nand provided an approach to comprehensively utilize the lignocellulosic\nsugars.