Efficient conversion of lignocellulosic biomass requires biocatalysts able to tolerate inhibitors produced by many pretreatment processes. Recombinant Zymomonas mobilis 8b, a recently developed integrant of Zymomonas mobilis 31821(pZB5), tolerated acetic acid up to 16 g l(-1) and achieved 82%-87% (w/w) ethanol yields from pure glucose/xylose solutions at pH 6 and temperatures of 30degreesC and 37degreesC. An ethanol yield of 85% (w/w) was achieved on glucose/xylose from hydrolysate produced by dilute sulfuric acid pretreatment of corn stover after an 'overliming' process was used to improve hydrolysate fermentability.