Low-dosage hydrophobically modified copolymers as effective promoters in enzymatic hydrolysis of lignocellulosic biomass.

Abstract

Amphiphilic surfactants have shown promise as enhancers for lignocellulosic enzymatic saccharification, but conventional additives often perform poorly at low dosage. To overcome this limitation, we engineered poly(AM-b-Sty) via micellar polymerization, incorporating hydrophobic styrene (Sty) units into a hydrophilic acrylamide (AM) backbone. This design increases the additive's affinity for lignin surfaces while minimizing nonproductive cellulase adsorption onto residual lignin. The optimized copolymer (15.4 mol% Sty) outperformed conventional additives (e.g., PEG, CTAB, Tween-80, BSA), boosting glucose yields from 37.6% to 67.7% at low loading (0.5 g/L, 25 mg/g glucan) and cutting enzyme dosage by 67% (to 5 FPU/g glucan). Mechanistic studies showed that hydrophobic chains in poly(AM-b-Sty) increased its adsorption capacity on lignin by 53-fold compared to the polymer without hydrophobic segments, while the AM chains formed a hydrated barrier on lignin surfaces. Consequently, nonproductive cellulase binding was reduced by 65%. Furthermore, hydrophobic units synergistically formed protective layers at the air-liquid interface and stabilized cellulase secondary structure, minimizing activity loss under environmental stresses. This work establishes hydrophobicity-engineered copolymers as effective lignin-blocking agents and provides mechanistic insights for rational additive design.