Hydrophilicity Regulation of Styrene-Based Copolymers to Promote the Enzymatic Saccharification Efficiency by Dually Protecting Cellulases and Blocking Residual Lignin

Nonproductive adsorption behavior of residual lignin on cellulase has long hindered lignocellulosic biomass enzymatic saccharification. In this study, a strategy of hydrophilicity regulation of styrene-based copolymers was developed to improve the enzymatic saccharification efficiency by specifically acting on cellulases and blocking residual lignin. Styrene-based copolymers with 2-acrylamido-2-methylpropanesulfonate (ST-co-AMPS or SA), varying in molecular weight and hydrophilicity, were synthesized. At pH 4.8 and 10 FPU/glucan cellulase dosage, adding 0.1 g/g-substrate SA8-32 (initiator dosage = 8%, ST% = 32%) boosted the sugar yield from 45.6 to 83.4%. When the pH increased to 5.5, SA4-16 addition further raised the yield to 94%. Quartz crystal microbalance and atomic force microscopy analyses revealed that ST-co-AMPS directly interacted with cellulase to form complexes while also blocking residual lignin. Fluorescence spectrometer analysis showed SA-cellulase complexes reduced nonproductive adsorption via hydrogen bonding and van der Waals forces. Given the demand for efficient lignocellulosic bioconversion in sustainable biorefineries, ST-co-AMPS shows great potential as an additive to enhance lignocellulose enzymatic saccharification.