Genetic engineering pentose fermentation

Bacteria will ferment pentoses to ethanol plus mixed acids [4], and various researchers have genetically engineered bacteria to improve ethanol production from pentoses. However, most industrial ethanol fermentations use S. cerevi-... 

Whereas the fermentation of glucose can be carried out efficiently, the bioconversion of the pentose fraction out of lignocellulosic feedstocks and residues presents a challenge. A lot of attention has therefore been focused on genetically engineering strains that can efficiently utilize both glucose and pentose and convert them to useful compounds. The metabolic engineering objectives so far have... 

The yeast Saccharomyces cerevisiae) enzymes are specific to six-carbon sugars, but wood and other forms of biomass also contain large quantities of pentose sugars, especially xylose in hardwoods. The pentoses are not fermentable to ethyl alcohol with conventional yeasts. However, researchers at the U.S.D.A. Forest Products Laboratory have discovered a xylose-fermenting yeast (Candida tropicalis). Thus it now is possible to convert all wood sugars to ethyl alcohol with a combination of yeasts. Isolation of the specific enzymes and genetic engineering of the enzymes could dramatically improve the efficiency of this conversion. 

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