Tuesday, July 31, 2007 - 8:30 AM
S75
Genomic engineering of Saccharomyces cerevisiae for biomass conversion to ethanol
Z. Lewis Liu, US Department of Agriculture, ARS, National Center for Agricultural Utilization Research, 1815 N. University, Peoria, IL 61604
The economics of fermentation-based bioprocesses rely extensively on the performance of microbial biocatalysts in industrial application. Development of yeast strains that can efficient utilize heterogeneous sugars and withstand stress conditions in bioethanol conversion process is the key for sustainable, economic and cost-competitive lignocellulosic biomass conversion to ethanol. However, many of the industrially interesting microorganisms obtained thus far are not robust and able to efficiently utilize diversified sugars derived from the biomass. We recently developed a tolerant ethanologenic yeast strain 12HF10 by directed evolutionary adaptation that in situ detoxified furfural and HMF, and produced normal yield of ethanol in 48 hours, while a wild type S. cerevisiae control failed to establish a culture. Strain 12HF10 did not require a pre-build biomass but functioned as an initial inoculum to build a culture and complete the fermentation. Strains tolerant to HMF and able to use xylose were also obtained through the directed evolutionary adaptation method under the laboratory settings. Based on documented yeast inner genetic potential, adaptation with desirable characteristics can be accomplished. Enhancement of genetic background of the ethanologenic yeast is needed as necessary by recombinant genetic engineering. The enhanced laboratory procedures significantly speed up biological evolutionary adaptation events to the stress condition and maintain the desirable ethanol production characteristics of the yeast. Studies on genomic mechanisms of the comprehensively integrated functions are under way. A comprehensive approach of genomic engineering will allow us to meet the challenges for efficient lignocellulosic biomass conversion to ethanol in a decade and beyond.