Specificity of feruloyl esterases for water-extractable and water-unextractable feruloylated polysaccharides: influence of xylanase

Representatives of three types of feruloyl esterases were examined for their ability to release mono- and di-meric ferulic acid from water-extractable and water-unextractable cereal cell wall material, either alone or in the presence of a family 10 or family 11 xylanase. A type-C feruloyl esterase from Talaromyces stipitatus (TsFaeC) released 100% of the ferulic acid from water-extractable wheat endosperm arabinoxylan when acting in combination with a xylanase from Trichoderma longibrachiatum. The type-A esterase from Aspergillus niger, AnFaeA, was most effective in releasing ferulic acid from wheat bran and brewers' spent grain, with over 50% of the available ferulic acid being released from wheat bran in the presence of a xylanase from Bacillus subtilis. In general, family 11 xylanases were the preferred synergistic partners with feruloyl esterases for the release of ferulic acid, while family 10 xylanases were preferred for the liberation of diferulic acid, with only the 5,5' form being released by the action of AnFaeA alone. This suggests that ferulic acid may be located in regions of low substitution on arabinoxylans while the 5,5' diferulate moiety is located in more branched regions of the xylan chain. (C) 2003 Elsevier Ltd. All rights reserved.