Submitted to: Book Chapter
Publication Type: Book / chapter
Publication Acceptance Date: 11/5/2007
Publication Date: 9/18/2009
Citation: Liu, Z., Song, M. 2009. Genomic adaptation of Saccharomyces cerevisiae to inhibitors involving biomass conversion to ethanol. In: Rai, M., Bridge, P.D., editors. Applied Mycology. Chapter 8. Wallingford, United Kingdom: CAB International. p. 136-155. Interpretive Summary:
Technical Abstract: The dose-dependent inhibition of the ethanologenic yeast allowed its potential adaptation to the inhibitors to transform furfural and 5-hydroxymethylfurfural (HMF) into less toxic compounds of furan methanol (FM) and furan-2,5-dimethanol (FDM), respectively. The isolation and identification of HMF metabolic conversion end product as FDM has clarified existing literature and provides a basis for metabolic profiling studies of yeast on inhibitor stress tolerance. A genomic approach is needed for efficient improvement of ethanologenic yeast performance. For high throughput genomic expression studies, the proper application of quality control measurements is critical to ensure the reliability and reproducibility of expression data, and allows data confirmation and comparison. Gene expression responses of the ethanologenic yeast to furfural and HMF stress during the fermentation were not transient. In fact, the yeast adaptation to furfural and HMF was a continued dynamic process involving multiple genes at the genome level. With the aid of the comprehensive and updated yeast database, we can readily explore global transcriptome profiling of the ethanologenic yeast and provide additional insights into the complexity of adaptation to the inhibitor stress. However, a great deal of knowledge remains unknown. Among the significant genes involved in the adaptation, some genes were found to have limited annotation of defined functions. Challenges remain to assign complete functions, draw meaningful conclusions from the complex relationships, and assess biological confirmations of gene regulatory networks. Global transcriptome profiling of the tolerant strain is under investigation. Key function genes and relevant regulatory components responsible for the biotransformation and detoxification of the inhibitor will be characterized. With system computation modeling of the gene regulatory network, a more accurate account of the genomic mechanism on inhibitor detoxification and tolerance of ethanologenic yeast can be expected. Multiple gene mediated aldehyde reduction has been demonstrated as a mechanism of detoxification of furfural and HMF. The genomic mechanism of stress tolerance to furfural, HMF, and the inhibitory complex involved in bioethanol conversion will be further elucidated to aid more robust strain design and development in the future. Directed evolutionary genomic adaptation focused on improvement of specific molecular functions and metabolic dynamics performed under laboratory settings is a powerful means for improvement and development of desirable strains. Such technology combined with traditional genetic studies will bring us to a new horizon for understanding the ethanologenic yeast. A comprehensive genomic engineering approach will allow us to meet the challenges for efficient lignocellulosic biomass conversion to ethanol in a decade and beyond.