Economical biofuel production from plant biomass requires the conversion of both cellulose and hemicellulose in the plant cell wall. The best industrial fermentation organism, the yeast has been developed to utilize xylose by heterologously expressing either a xylose reductase/xylitol dehydrogenase (XR/XDH) pathway or a xylose isomerase (XI) pathway. Although it has been proposed that the optimal means for fermenting xylose into biofuels would use XI instead of the XR/XDH pathway, no clear comparison of the best publicly-available yeast strains engineered to use XR/XDH or XI has been published. We therefore compared two of the best-performing engineered yeast strains in the public domain-one using the XR/XDH pathway and another using XI-in anaerobic xylose fermentations. We find that, regardless of conditions, the strain using XR/XDH has substantially higher productivity compared to the XI strain. By contrast, the XI strain has better yields in nearly all conditions tested.
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| http://dx.doi.org/10.1016/j.btre.2016.01.003 | DOI Listing |
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Article Synopsis
- Xylose, a sugar found in plant biomass, can be converted to bioethanol, but its fermentation is challenging when glucose is present, as both sugars compete for cellular intake.
- Research involved engineering a yeast strain (Saccharomyces cerevisiae) to enhance the conversion of xylose to xylulose outside the cell, improving xylose utilization even alongside glucose.
- The engineered enzyme from Piromyces sp. showed increased activity under acidic conditions, resulting in a 7-20% increase in xylose consumption and a 15-20% boost in ethanol production compared to previous methods.
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