Effect of cellulase on the UCST behavior of sulfobetaine zwitterionic surfactants and the cellulase recovery mechanism

Abstract

The recovery of cellulase at room temperature by adding recyclable thermoresponsive zwitterionic surfactants is more significant for reducing the cost of the production of cellulosic ethanol. Sulfobetaines can exhibit a thermoresponsive upper critical solution temperature (UCST) in acetate buffer solutions. Here, the performance was optimised by adjusting the carbon chain length and concentration of sulfobetaines. As an example, octadecyl sulfobetaine (SB3-18) showed sensitive UCST-responsive performance at 25–50 °C (0–0.40 g L⁻¹). Interestingly, SB3-18 and cellulase precipitated together, and 0.20 g L⁻¹ SB3-18 could recover 58.9% of cellulase by cooling down to 25 °C. In addition, SB3-18 could recover more than 50% of cellulase during the enzymatic hydrolysis of corncob residues (CCRs). Finally, hydrophobic interaction is the main driving force for the recovery of cellulase as revealed by quartz crystal microbalance by the dissipation (QCM-D) test. In this work, the process of recovering cellulase is simple and green and does not require acids and alkalis. This recovery method is applicable for the separation and purification of some other hydrophobic proteins.