COMPARISON OF NATURAL HEMICELLULOSE AND CHEMICALLY ACETYLATED XYLAN AS SUBSTRATES FOR THE DETERMINATION OF ACETYL-XYLAN ESTERASE-ACTIVITY IN ASPERGILLI

Native hemicellulose obtained as a result of an aqueous phase thermochemical treatment of aspen wood was tested as a substrate for the determination of acetyl-xylan esterase activities of a number of Aspergilli cultures. The native hemicellulose contained about 60% xylose, of which every two out of three xylose residues were acetylated. Results obtained using the native hemicellulose and chemically acetylated xylan were comparable for the majority of Aspergilli tested, except the enzyme preparations obtained from A. japonicus and A. niger ATTC strain 10864, which were significantly more active on native hemicellulose than on chemically acetylated xylan. The results obtained using 4-nitrophenyl acetate as a substrate showed no relation with those obtained using native hemicellulose or chemically acetylated xylan as substrates. Among the various species and strains of Aspergilli tested, A. japonicus, A. niger ATCC no. 10864, and A. versicolor produced the highest amounts of acetyl-xylan esterase, and the production of this enzyme was greatly induced by the presence of cellulose or xylan in the medium. © 1990.