Modified Yeast Show Improved Xylose Fermentation and Toxin Tolerance


Bleaching plant material with alkaline hydrogen peroxide (AHP) is an old process used for papermaking. Several decades ago researchers suggested that this method also could be used in biofuel production. The method involves treating switchgrass or corn stover with hydrogen peroxide under basic conditions. However before enzymatic conversion can yield useful quantifies of glucose and xylose the pH of the mixture must be adjusted to acidic conditions. Unfortunately this pretreatment produces molecules like p-Coumaric acid and Ferulic acid which are toxic to fermenting microbes. This problem undercuts the practicality of AHP in an industrial biofuel setting. A UW–Madison researcher and others have developed genetically modified S. cerevisiae strains capable of xylose fermentation and better able to tolerate toxins associated with biomass pretreatment. The strains called GLBRCY73 and GLBRCY87 were evolved in the presence of increasing amounts of p-Coumaric and Ferulic acids. Desirable specimens were selected based on strong growth characteristics. Applications: Industrial ethanol production


1) Good xylose fermentation 2) More tolerant to toxins produced during biomass pretreatment 3) Strains don’t require hydrolysate purification steps prior to fermentation 4) Could lower biofuel manufacturing costs 5) Strains are hardy and easy to work with on an industrial scale

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