Submitted to: American Society for Microbiology Meeting
Publication Type: Abstract only
Publication Acceptance Date: 5/21/2009
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Lignocellulosic biomass conversion inhibitors furfural and HMF inhibit microbial growth and interfere with subsequent fermentation of ethanol. Numerous yeast genes were found to be associated with the inhibitor tolerance. However, little is known about system mechanisms of the tolerance and detoxification of furfural and HMF. Using a robust standard for absolute mRNA quantification assay and a recently developed tolerant ethanologenic yeast Saccharomyces cerevisiae NRRL Y-50049, we investigated pathway-based transcription profiles relevant to the yeast tolerance and the inhibitor detoxification. Tolerant strain Y-50049 displayed enriched genetic background with higher abundant transcripts of at least 16 genes than a non-tolerant parental strain Y-12632. Under the inhibitor-challenged conditions, Y-50049 was able to withstand and in situ detoxify furfural and HMF and produce ethanol within 48 hours; while Y-12632 failed to function until 65 hours after incubation. We present unique glucose metabolic pathways of Y-50049 describing mechanisms of the tolerance and the in situ detoxification of furfural and HMF. The enhanced expression of ZWF1 appeared to drive glucose metabolism in favor of pentose phosphate pathway over glycolysis at earlier steps of glucose metabolisms. Cofactor NAD(P)H generation steps were likely accelerated by enzymes encoded by ZWF1, GND1, GND2, TDH1, and ALD4. NAD(P)H-dependent aldehyde reductions, including conversion of furfural and HMF, in return, provided sufficient NAD(P)+ for NAD(P)H regeneration in the yeast detoxification pathways. Enriched genetic background and a well maintained redox balance through reprogrammed expression responses of Y-50049 were accountable for the acquired tolerance and detoxification of furfural to furan methanol and HMF to furan dimethanol.