Sustainable 2-keto-L-gulonic acid biosynthesis via single-strain one-step fermentation

L-ascorbic acid (vitamin C) is an essential antioxidant molecule that maintains normal physiological functions in humans. Currently, industrial production relies primarily on a three-strain, two-step fermentation process to produce 2-keto-L-gulonic acid (2-KLG), the direct precursor of vitamin C. 2-KLG is then converted to vitamin C through chemical lactonization. However, this process is limited by prolonged fermentation cycles, poor stability of the mixed-culture system, and complex process control. In recent years, engineered single-strain platforms capable of one-step 2-KLG biosynthesis have emerged as a promising strategy for more sustainable vitamin C production. Nevertheless, the efficiency of L-sorbose-to-2-KLG conversion in this system remains low, making it a major bottleneck to further improving 2-KLG production. This review summarizes recent advances on single-strain, one-step fermentation systems using Gluconobacter oxydans as the chassis strain. It focuses on strategies including genetic tool development, metabolic engineering, and key enzyme optimization. The review aims to provide a theoretical basis and technical reference for optimizing and industrializing green biomanufacturing systems for vitamin C.