Efficient fermentation of xylose to ethanol at high formic acid concentrations by metabolically engineered Saccharomyces cerevisiae.
Recombinant yeast strains highly tolerant to formic acid during xylose fermentation were constructed. Microarray analysis of xylose-fermenting Saccharomyces cerevisiae strain overexpressing endogenous xylulokinase in addition to xylose reductase and xylitol dehydrogenase from Pichia stipitis revealed that upregulation of formate dehydrogenase genes (FDH1 and FDH2) was one of the most prominent transcriptional events against excess formic acid. The quantification of formic acid in medium indicated that the innate activity of FDH was too weak to detoxify formic acid. To reinforce the capability for formic acid breakdown, the FDH1 gene was additionally overexpressed in the xylose-metabolizing recombinant yeast. This modification allowed the yeast to rapidly decompose excess formic acid. The yield and final ethanol concentration in the presence of 20 mM formic acid is as essentially same as that of control. The fermentation profile also indicated that the production of xylitol and glycerol, major by-products in xylose fermentation, was not affected by the upregulation of FDH activity.
Organization of Advanced Science and Technology, Kobe University, 1-1 Rokkodaicho, Nada-ku, Kobe, Hyogo 657-8501, Japan.
Tomohisa
T
Hasunuma
Kyung-mo
KM
Sung
Tomoya
T
Sanda
Kazuya
K
Yoshimura
Fumio
F
Matsuda
Akihiko
A
Kondo
D000449:Aldehyde Reductase / Q000235:genetics / Q000378:metabolism; D050542:D-Xylulose Reductase / Q000235:genetics / Q000378:metabolism; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D005561:Formates / Q000378:metabolism*; D005818:Genetic Engineering; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism; D010843:Pichia / Q000201:enzymology / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D014994:Xylose / Q000378:metabolism*
D005561:Formates; C030544:formic acid; D000431:Ethanol; D014994:Xylose; D000449:Aldehyde Reductase; D050542:D-Xylulose Reductase; D017853:Phosphotransferases (Alcohol Group Acceptor); C032700:xylulokinase