ARS | Publication request: Functional genomic studies lead in situ detoxification of fermentation inhibitors for low-cost cellulosic ethanol production

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 21, 2008
Publication Date: N/A

Technical Abstract: Renewable biomass, including lignocellulosic materials and agricultural residues, are low-cost materials for bioethanol production. However, significant challenges exist for efficient cost-effective conversion of cellulosic ethanol. One technical barrier is the stress conditions caused by toxic compounds that interfere with microbial growth and subsequent fermentation. Furfural and 5-hydroxymethylfurfrual (HMF) are the most potent and representative inhibitors derived from dehydration of pentoses and hexoses during biomass degradation by dilute acid treatment. These compounds reduce enzymatic activities, break down DNA, inhibit protein and RNA synthesis, and damage cell wall of yeast. Tolerant strains are needed but few are currently available. Using genomic studies of ethanologenic yeast Saccharomyces cerevisiae, we identified over 300 genes significantly involved in the inhibitor stress conditions, characterized gene regulatory networks to the stress response, identified new genes and novel genes that contribute to the in situ detoxification, and proposed inhibitor detoxification pathways relevant to glycolysis and ethanol production. In addition, we proposed genomic adaptation and developed more tolerant strains using directed adaptation strategy and protein engineering methods. These newly developed tolerant strains demonstrate significantly increased enzymatic activity to detoxify furfural and HMF and produce ethanol without increased cell mass or nursing fermentation conditions. Our results suggest that it is possible to in situ detoxify furfural and HMF by ethanologenic yeast S. cerevisiae; and a mechanism of the detoxification is due to NAD(P)H-dependent aldehyde reduction, but not furan conversion, accomplished through multiple gene-mediated functions.