Patent ID: 9624517
Date: 2017-04-18
CPC Classifications: C12P

Claim:
1. An Escherichia coli microorganism capable of converting a mixture of hemicellulosic sugars, wherein the sugars are selected from the group consisting of xylose, arabinose and combinations thereof, wherein the mixture of hemicellulosic sugars have a xylose:arabinose ratio of approximately 3:1 or better, wherein the microorganism comprises: (a) a mutant xylose reductase (XR), wherein the mutant xylose reductase comprises SEQ ID NO:20; wherein the mutant XR has a higher selectivity for xylose than arabinose, and (b) an inactivated glucose-specific phosphotransferase transport system gene (PtsG), or a cyclic adenosine monophosphate receptor gene (CRP) mutation that de-represses xylose metabolism under aerobic conditions; and (c) optionally, a D-xylose transporter gene (xylE) under the control of an araBAD promoter; wherein there is near complete depletion of arabinose, and wherein conversion is by fermentation to xylitol with little or no arabitol present in the final fermentation broth.