Improved Xylitol Production from d‑Arabitol by Enhancing the Coenzyme Regeneration Efficiency of the Pentose Phosphate Pathway in Gluconobacter oxydans

Gluconobacter oxydans is used to produce xylitol from d-arabitol. This study aims to improve xylitol production by increasing the coenzyme regeneration efficiency of the pentose phosphate pathway in <i>G. oxydans</i>. Glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH) were overexpressed in <i>G. oxydans</i>. Real-time PCR and enzyme activity assays revealed that G6PDH/6PGDH activity and coenzyme regeneration efficiency increased in the recombinant <i>G. oxydans</i> strains. Approximately 29.3 g/L xylitol was obtained, with a yield of 73.2%, from 40 g/L d-arabitol in the batch biotransformation with the <i>G. oxydans</i> PZ strain. Moreover, the xylitol productivity (0.62 g/L/h) was 3.26-fold of the wild type strain (0.19 g/L/h). In repetitive batch biotransformation, the <i>G. oxydans</i> PZ cells were used for five cycles without incurring a significant loss in productivity. These results indicate that the recombinant <i>G. oxydans</i> PZ strain is economically feasible for xylitol production in industrial bioconversion