Abstract:

The influence of overexpression of glucose 6-phosphate dehydrogenase (G6PDH) gene, g6pd, on xylitolbiosynthesis in Candida tropicalis was investigated. The gene g6pd was cloned from Candida tropicalis CT16 and insertedinto a yeast expression vector pYES-pgk, generating a recombinant expression vector pYES-pgk-g6pd, which was thenintroduced into C. tropicalis CT16 by the LiAc/ssDNA/PEG transformation method, resulting in over-expression of theg6pd gene. The fermentation results showed that the G6PDH activity was increased by 300%, and a maximum xylitol yieldof 79.90 g/L was achieved in the recombinant strain SYG5 harboring pYES-pgk-g6pd after 62 h of fermentation. Comparedto the wild type strain C. tropicalis CT16, the yield and productive rate of xylitol in strain SYG5 were increased by 11.30%and 44.91%, respectively. These results indicate that increasing the expression level of the gene g6pd significantly enhancesxylitol production and that the G6PDH plays a key role in the biosynthesis pathway of xylitol in C. tropicalis.

Key words: Candida tropicalis, glucose 6-phosphate dehydrogenase (G6PDH), gene g6pd over-expression, xylose, xylitol