Synthesis of highly pH-responsive lignin-based polycarboxylic acids and their application in cellulase recovery

Recycling cellulase by using pH-responsive additives is an effective strategy for reducing the cost of lignocellulosic enzymatic hydrolysis. Traditional pH-responsive additives have limitations, including an insensitive pH response or weak binding to enzyme proteins, which restrict their industrial applications. The strong binding property of lignin to enzyme proteins was used to construct a series of ultra-high pH-responsive lignin-modified copolymers containing amide and carboxylic acid groups (L-CPM), which were obtained by using lignin cross-link pH-sensitive prepolymers containing amide and carboxylic acid groups (CPM). The pH responsiveness of L-CPM was used to recycle cellulase. 3.0 g/L of L-CPM-3 was added to the enzymatic hydrolysis system of corncob residues (CCR) (pH = 5.0). After enzymatic hydrolysis, 60 % of the cellulase amount was saved when adjusting the pH value of the hydrolyzate from 5.0 to 4.4. In this work, ultra-high pH-responsive L-CPM was used to recover cellulase, achieving efficient cellulase recycling in a narrow pH range. This provides a new strategy for reducing the cost of lignocellulosic enzymatic hydrolysis and realizing high-value utilization of industrial lignin.