Enhancement of xylitol production in Candida tropicalis

In this study, gk gene was disrupted from xylitol dehydrogenase gene (XYL2) knockout C. tropicalis strain BSXDH-3. The resulting strain was incapable to grow on glycerol. The cells growth on glycerol was resumed by co-expression of gcy1, 2 and 3 genes from Scheffersomyces stipitis under the control of C. tropicalis glyceraldehydes-3-phosphate dehydrogenase (GAPDH) promoter. NADPH-dependent xylitol production was higher in the engineered strain, termed IA-3 , than in BSXDH-3. The pentose phosphate pathway (PPP) is a major basis of NADPH biosynthesis in C. tropicalis. In order to increase xylitol production rate, xylitol dehydrogenase gene (XYL2)-disrupted C. tropicalis strain BSXDH-3 was engineered to co-express zwf and gnd genes, which respectively encode glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6-PGDH), under the control of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) promoter. NADPH-dependent xylitol production was higher in the engineered strain, termed "PP", than in BSXDH-3. This is the first report of increased metabolic flux toward glycerol metabolic and PPP in C. tropicalis for NADPH regeneration and enhanced xylitol production.

Autorentext

Dr. Irshad Ahmad has btained his Ph.D degree in Biological Sciences from Korea Advanced Institute of Science and Technology in 2011. Since then he joined University of Malakand as Assistant Professor of Biotechnology. He is the author of several articals published in reputed journals and is a member of different international working groups.