The level of glucose-6-phosphate dehydrogenase activity strongly influences xylose fermentation and inhibitor sensitivity in recombinant Saccharomyces cerevisiae strains.
Disruption of the ZWF1 gene encoding glucose-6-phosphate dehydrogenase (G6PDH) has been shown to reduce the xylitol yield and the xylose consumption in the xylose-utilizing recombinant Saccharomyces cerevisiae strain TMB3255. In the present investigation we have studied the influence of different production levels of G6PDH on xylose fermentation. We used a synthetic promoter library and the copper-regulated CUP1 promoter to generate G6PDH-activities between 0% and 179% of the wild-type level. G6PDH-activities of 1% and 6% of the wild-type level resulted in 2.8- and 5.1-fold increase in specific xylose consumption, respectively, compared with the ZWF1-disrupted strain. Both strains exhibited decreased xylitol yields (0.13 and 0.19 g/g xylose) and enhanced ethanol yields (0.36 and 0.34 g/g xylose) compared with the control strain TMB3001 (0.29 g xylitol/g xylose, 0.31 g ethanol/g xylose). Cytoplasmic transhydrogenase (TH) from Azotobacter vinelandii has previously been shown to transfer NADPH and NAD(+) into NADP(+) and NADH, and TH-overproduction resulted in lower xylitol yield and enhanced glycerol yield during xylose utilization. Strains with low G6PDH-activity grew slower in a lignocellulose hydrolysate than the strain with wild-type G6PDH-activity, which suggested that the availability of intracellular NADPH correlated with tolerance towards lignocellulose-derived inhibitors. Low G6PDH-activity strains were also more sensitive to H(2)O(2) than the control strain TMB3001.
Jeppsson
Marie
M
Department of Applied Microbiology, Lund University, PO Box 124, 221 00 Lund, Sweden.
Johansson
Björn
B
Jensen
Peter Ruhdal
PR
Hahn-Hägerdal
Bärbel
B
Gorwa-Grauslund
Marie F
MF
D000085:Acetates / Q000378:metabolism; D001483:Base Sequence; D002352:Carrier Proteins; D002482:Cellulose / Q000378:metabolism; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D000431:Ethanol / Q000378:metabolism; D005285:Fermentation; D015966:Gene Expression Regulation, Fungal; D005954:Glucosephosphate Dehydrogenase / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D005990:Glycerol / Q000378:metabolism; D008031:Lignin / Q000378:metabolism; D008668:Metallothionein / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000502:physiology; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D014170:Transformation, Genetic / Q000502:physiology; D014993:Xylitol / Q000378:metabolism; D014994:Xylose / Q000378:metabolism*
D000085:Acetates; C500769:CUP1-1 protein, S cerevisiae; D002352:Carrier Proteins; D004271:DNA, Fungal; C007121:copper thionein; C036909:lignocellulose; D000431:Ethanol; D002482:Cellulose; D008031:Lignin; D008668:Metallothionein; D014994:Xylose; D005954:Glucosephosphate Dehydrogenase; D005990:Glycerol; D014993:Xylitol