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Applied and Environmental Microbiology, December 2005, p. 7866-7871, Vol. 71, No. 12
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.12.7866-7871.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Cofactor Dependence in Furan Reduction by Saccharomyces cerevisiae in Fermentation of Acid-Hydrolyzed Lignocellulose

Anneli Nilsson,1 Marie F. Gorwa-Grauslund,2 Bärbel Hahn-Hägerdal,2 and Gunnar Lidén1*

Department of Chemical Engineering, Lund University, P.O. Box 124, S-221 00 Lund, Sweden,1 Department of Applied Microbiology, Lund University, P.O. Box 124, S-221 00 Lund, Sweden2

Received 22 December 2004/ Accepted 14 August 2005

A decreased fermentation rate due to inhibition is a significant problem for economic conversion of acid-pretreated lignocellulose hydrolysates to ethanol, since the inhibition gives rise to a requirement for separate detoxification steps. Together with acetic acid, the sugar degradation products furfural and 5-hydroxymethyl furfural are the inhibiting compounds found at the highest concentrations in hydrolysates. These aldehydes have been shown to affect both the specific growth rate and the rate of fermentation by yeast. Two strains of Saccharomyces cerevisiae with different abilities to ferment inhibiting hydrolysates were evaluated in fermentations of a dilute acid hydrolysate from spruce, and the reducing activities for furfural and 5-hydroxymethyl furfural were determined. Crude cell extracts of a hydrolysate-tolerant strain (TMB3000) converted both furfural and 5-hydroxymethyl furfural to the corresponding alcohol at a rate that was severalfold higher than the rate observed for cell extracts of a less tolerant strain (CBS 8066), thereby confirming that there is a correlation between the fermentation rate in a lignocellulosic hydrolysate and the bioconversion capacity of a strain. The in vitro NADH-dependent furfural reduction capacity of TMB3000 was three times higher than that of CBS 8066 (1,200 mU/mg protein and 370 mU/mg protein, respectively) in fed-batch experiments. Furthermore, the inhibitor-tolerant strain TMB3000 displayed a previously unknown NADH-dependent reducing activity for 5-hydroxymethyl furfural (400 mU/mg protein during fed-batch fermentation of hydrolysates). No corresponding activity was found in strain CBS 8066 (<2 mU/mg). The ability to reduce 5-hydroxymethyl furfural is an important characteristic for the development of yeast strains with increased tolerance to lignocellulosic hydrolysates.

* Corresponding author. Mailing address: Department of Chemical Engineering, Lund University, P.O. Box 124, S-221 00 Lund, Sweden. Phone: 46-46-222-0862. Fax: 46-46-149156. E-mail: Gunnar.Liden{at}chemeng.lth.se.

Applied and Environmental Microbiology, December 2005, p. 7866-7871, Vol. 71, No. 12
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.12.7866-7871.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Miller, E. N., Jarboe, L. R., Yomano, L. P., York, S. W., Shanmugam, K. T., Ingram, L. O. (2009). Silencing of NADPH-Dependent Oxidoreductase Genes (yqhD and dkgA) in Furfural-Resistant Ethanologenic Escherichia coli. Appl. Environ. Microbiol. 75: 4315-4323 [Abstract] [Full Text]  
  • Nevoigt, E. (2008). Progress in Metabolic Engineering of Saccharomyces cerevisiae. Microbiol. Mol. Biol. Rev. 72: 379-412 [Abstract] [Full Text]  


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