Enzymic hydrolysis of water-soluble lignin-carbohydrate complexes from Populus deltoides: Effects of combinations of β-mannanases, xylanase, and acetyl xylan esterase

Abstract

Cooperativitiy between different, purified hemicelluloytic enzymes was examined using as substrates two lignin-carbohydrate complexes isolated from the water-soluble fractions of steam/aqueous thermo-mechanical treatment of Populus deltoides wood. The thermomechanical treatments were carried out at 177 and 218°C, and the material obtained from the lower-temperature treatment ( PD 177) was glucomannan-rich while that obtained from the higher-temperature treatment ( PD 218) was O-acetylxylan-rich. The lignin-carbohydrate complexes were choses as models for the action of hydrolytic enzymes in aiding the bleaching of pulp. Enzyme combinations had appreciable effects which included synergism, inhibition, and simple additivity, and the effect observed with a particular combination depended, in some instances, on the substrate. Combinations of a number of isozymes of Polyporus versicolor β-mannanase functioned as if each enzyme acte independently on PD 177, but both inhibitory and synergistic effects occurred with PD 218. Synergistic behavior was seen with combinations of Bacillus circulans xylanase and Schizophyllum commune acetyl xylan esterase activities, but these enzymes generally had little effect on β-mannanase activity. Enzymatic deacetylation had little effect on mannanase activity except for one of the mannanases, where inhibition occurred.