Proteinaceous inhibitors of xylanase naturally occur in cereals where they are involved in various roles in the plant defence metabolism. This study focused on the inhibitors of xylanase present in local rye cultivars, and their influence on the efficiency of the fermentation processes during bioethanol production from rye residues in comparison with common wheat. Different origin xylanases from Thermomyces lanuginosus and Trichoderma reesei were the objects of the investigations. Kinetic studies of these xylanases in the presence of proteins with inhibitory activity indicated that Th. lanuginosus was found more sensitive to proteinaceous xylanase inhibitors presented in rye than T. reesei. The highest yield of xylose and arabinose was achieved by adding T. reesei to cell wall substrates, while Th. lanuginosus converted to arabinoxylans only into xylooligosaccharides and monosaccharide were not released. The activity of xylanase in composition with alpha-amylase and glucoamylase was selected to achieve a higher ethanol yield in the distillate. It improved the quality of bioethanol by increasing the content of ethanol and decreasing the concentrations of propanol, isobutanol, isoamyl and amyl alcohols and the methanol concentration. No significant differences were found between the contents of ethanol from different type of bran. (C) 2011 Elsevier B.V. All rights reserved.