Yeast Strain Could Help Fast-Track Biofuel Production

Stephen Hughes, A USDA Agricultural Research Service (ARS) molecular biologist, has developed a yeast that makes ethanol from both five-carbon and six-carbon sugars without needing oxygen. This development could speed up industrial ethanol production because oxygen level control has been a difficult part of the process.

Hughes' yeast strain doesn’t require oxygen to grow on xylose, a five-carbon plant sugar. The new yeast doesn’t directly convert large quantities of xylose into ethanol, according to an ARS press release. Instead, xylose provides energy the yeast needs to grow and reproduce without oxygen, making more of the yeast available for fermentation, and the rate of ethanol conversion increases.

To begin this research, Hughes developed a yeast strain containing a gene that makes an enzyme for converting xylose into ethanol. He added another gene to the strain so that the yeast could metabolize the xylose more efficiently.

Then Hughes created 6,113 different yeast strains that contained both genes and screened all of the strains for traits for enhanced ethanol production. He found seven strains that were able to convert both glucose and xylose into ethanol without oxygen.

But the seven yeast strains had relatively low rates of xylose fermentation, so Hughes and his group screened the strains for genes that could step up xylose’s contribution to ethanol conversion in other ways. They found five genes associated with the enzyme that converts xylose into ethanol, and confirmed that these five genes play a critical role in yeast cell growth.

Hughes works at the ARS National Center for Agricultural Utilization Research in Peoria, Ill. This research has been published in the August 2009 Journal of the Association of Laboratory Automation theme issue on biofuels research.

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