Adsorption behavior of two glucanases on three lignins and the effect by adding sulfonated lignin

The adsorption behaviors of two glucanases, TvEG and TrCel7A, on three lignins were investigated. Three lignins were isolated from raw aspen and its pretreated solid residue. The isolated lignins were labeled as Asp-MWL, DA-MWL (pretreated by dilute acid), and GL-MWL (pretreated by green liquor), respectively. The surface properties of lignins and spin-coated lignin films were characterized by zeta potential, atomic force microscope (AFM) and contact angle. The enzyme adsorption behavior was monitored by quartz crystal microbalance (QCM) and fluorescence spectrometer. TlCel7A had similar adsorption capacities on the three lignin films but were higher than those of TvEG. The TrCel7A adsorptions on the three lignin films were affected by synergistic effect of electrostatic and hydrophobic interaction while the TvEG adsorptions on the three lignin films were mainly dominated by hydrophobic action. The adsorption capacities of TlCel7A and TvEG on the three lignin films were decreased by adding SL. Plausible explanation was that the SL and glucanase formed a complex with more negative charges, which suppressed the adsorption of glucannase on lignin through electrostatic repulsion. It also explained the improved enzymatic hydrolysis efficiency of lignocellulose upon adding SL.