Experimental evolution reveals an effective avenue to release catabolite repression via mutations in XylR

Significance Lignocellulosic biomass is a promising renewable feedstock for microbial production of fuels and chemicals. D-glucose and D-xylose are the most abundant sugars in lignocellulosic materials. Economically feasible bioconversion of lignocellulose requires simultaneous utilization of both sugars, which is primarily prevented by carbon catabolite repression. Here we characterize the genetic basis of three independent laboratory evolution trajectories for improved xylose fermentation and reveal an effective way to release carbon catabolite repression in Escherichia coli .