Synergy between endo/exo-glucanases and expansin enhances enzyme adsorption and cellulose conversion

Effective binding between cellulases and cellulose is essential for enzymatic hydrolysis of lignocellulose. Expansin can loosen the cellulose structure and can enhance the efficiency of cellulase. However, possible synergy between cellulases and expansin is not clear. In this work, the real-time adsorption of exoglucanases (Cel7A) or endoglucanases (Cel7B) with Bacillus subtilis expansin (BsEXLX1) and the enzymatic hydrolysis of cellulose were followed using quartz crystal microbalance with dissipation (QCM-D). Initial adsorption rate, adsorption capacity, and pseudo-steady-state rate of cellulose hydrolysis by Cel7A/Cel7B increased in the presence of BsEXLX1. When injecting Cel7A or Cel7B together with BsEXLX1 at a mass ratio of 1:1, the hydrolysis rate was almost 5 times the rate for Cel7A or Cel7B alone at 25 °C. These results increase our understanding of the real-time synergism between cellulases and expansin on cellulose, as well as the impact of their synergy on the enzymatic hydrolysis of cellulose.