Recycling Cellulase by a pH-Responsive Lignin-Based Carrier through Electrostatic Interaction

Abstract

Enzymatic conversion of lignocelluloses into fermentable sugars is a key step in producing liquid fuels and chemicals in an ecofriendly and sustainable manner. However, because of the large quantities of cellulase required in enzymatic hydrolysis, the high cellulase cost make the production cost of glucose still high. To reduce the overall production cost and achieve the comprehensive utilization of lignocelluloses. A new intensive production process for enzymatic saccharification was developed: lignin, the residue of lignocellulosic substrates after enzymatic hydrolysis, was modified to a pH-responsive carrier (pH-LC) by simple graft reactions and used to recycle cellulase through electrostatic interaction. pH-LC exhibited reversible soluble–insoluble property as solution pH changed, and it did not inhibit cellulase activity. By simply adjusting the pH of the solution contained pH-LC and cellulase, cellulase could be precipitated or dissolved for recycling. pH-LC could recover more than 90% of filter paper activity in solution for cellulase CTec2. During the enzymatic hydrolysis of corncob residue, pH-LC could not only recover more than 50% of cellulase but also increase the yield of glucose from 78.1% to 93.0%. This new process is not only green and convenient but also well integrated with existing processes and easily applied.