The synthesis of a UCST-type zwitterionic polymer for the efficient recycling of cellulase at room temperature

Abstract

In order to reduce the enzyme cost of lignocellulosic enzymatic hydrolysis, upper critical solution temperature (UCST) additives are used to recover and reuse cellulase by regulating the temperature. A sulfobetaine polymer, PSPE, showed a sensitive UCST response in buffer, and its UCST-performance was optimised by adjusting the molecular weight of the polymer. PSPE-3 (M_w = 355.1 kDa) was added to the cellulase buffer at 50 °C, and PSPE-3 and cellulase were co-precipitated by cooling to the room temperature of 25 °C. PSPE-3 and cellulase co-precipitated mainly through hydrophobic interactions via cooling. Compared with octadecyl sulfobetaine (SB3–18), PSPE-3 had a more sensitive UCST response and stronger cellulase recovery ability. Adding only 40% PSPE-3 (accounting for the mass fraction of cellulase) can save more than 50% cellulase in the enzymatic hydrolysis system of eucalyptus chips pre-treated with dilute acid (Eu-DA). However, for the Eu-DA system, adding 100% SB3–18 can only save about 30% of cellulase. In this work, efficient recycling of cellulase was achieved at room temperature by adding UCST-type PSPE. The process is green without consuming acid and alkali, and this work provides a new idea for reducing the production cost of cellulosic ethanol.