Adsorption of proteins involved in hydrolysis of lignocellulose on lignins and hemicelluloses

Protein adsorption onto eight lignocellulosic substances (six lignin preparations and two hemicelluloses) was investigated at pH 4.8 and at two different temperatures (4 °C and 45 °C). The kinetics of the adsorption of cellulase, xylanase, and β-glucosidase were determined by enzyme activity measurements. The maximum adsorption capacities, the affinity constants and the binding strengths varied widely and were typically higher for the lignins than for the carbohydrates. As indicated by BET and gel permeation chromatography, different substances had widely different surface area, pore size, weight average molecular weight, and polydispersity index, but these properties were difficult to relate to protein binding. In most cases, an increase in temperature from 4 °C to 45 °C and a low content of carboxylic acid groups, as indicated by Fourier-Transform Infra-Red (FTIR) spectroscopy, resulted in increased protein adsorption capacity, which suggests that hydrophobic interactions play an important role.