Copolymer with Tunable Cation Content as an Efficient Promoter in Enzymatic Saccharification of Lignocellulose

Nonproductive adsorption of cellulase is widely considered as the major roadblock to enzymatically hydrolyzing lignocellulosic biomass. Cationic additives present a promising avenue for mitigating the issue by effectively obstructing cellulase adsorption onto the lignin surface through enhanced electrostatic interactions with the negatively charged lignin, in contrast to nonionic additives. However, excessive positive charges carried by ionic additives can potentially hamper enzyme activity. To reconcile the dilemma, we synthesized a copolymer featuring modulatable cationic content via control over the ratio of nonionic and cationic units within the polymer backbone. Upon addition of 1.0 g/L of the resultant cationic copolymer, a notable enhancement in glucose release from 39 to 88% was observed, even at a low cellulase dosage of 5 FPU/g glucan. Remarkably, these cationic copolymers exhibit versatile applicability across diverse enzyme preparations, acid-treated lignocellulosic substrates, and highly solid saccharification systems. Furthermore, an enzyme saving of up to 80% was achieved. Mechanistic studies illuminated that this copolymer can not only attenuate the occurrence of irreversible binding between lignin and cellulase but also exert a favorable influence on enzyme activity. The adaptability of the copolymer’s cationic content endows it with the status of a promising and effective lignin-blocking additive, holding considerable potential for advancing the economic feasibility of biofuel production.