Effect of Sugars on the Real-Time Adsorption of Expansin on Cellulose

Abstract

Biological pretreatment is a safe and environmentally friendly method for disrupting recalcitrant ligno­cellulose structures. Expansin and expansin-like proteins are used to open up the cellulose structure and display significant synergism when mixed with cellulases that catalyze the breakdown of (hemi)­cellulose into sugars. However, the adsorption behavior of expansin in the presence of sugar products is yet unknown. In this work, we monitored the effects of various sugars on the real-time adsorption of Bacillus subtilis expansin (BsEXLX1) onto cellulose films using a quartz crystal microbalance with dissipation. Cellobiose and xylose at low concentrations enhanced BsEXLX1 adsorption, whereas they disrupted adsorption at higher concentrations. Arabinose and mannose continuously inhibited expansin adsorption with increasing concentration. No obvious influence of glucose and galactose on BsEXLX1 adsorption was found. Contact angle measurements and atomic force microscopy of cellulose upon BsEXLX1 adsorption in the presence of sugars showed that both hydro­philicity and roughness increased with BsEXLX1 treatment. These results give us the ability to modulate and control expansin adsorption and provide insights into effective expansin use during enzymatic hydrolysis of ligno­cellulose in biorefineries.

Expansin-mediated developmental and adaptive responses: A matter of cell wall biomechanics?

“…Other investigations of EXLX1 adsorption onto cellulose, using quartz crystal microbalance with dissipation (QCM-D), confirmed that cellobiose and xylose enhanced EXLX1 adsorption at low concentrations but inhibited it at high concentrations (Zhang et al, 2020 ). Monitoring real-time adsorption of endo/exo-glucanases with EXLX1 and the enzymatic hydrolysis of cellulose showed synergistic effects.…”

Biomacromolecular Characterizations Using State-of-the-Art Quartz Crystal Microbalance with Dissipation

“…They further carried out real-time QCM-D monitoring of expansin adsorption during the enzymatic hydrolysis of lignocellulose in biorefineries. These studies provide useful insights on highly efficient lignocellulose conversion. − …”

Real-Time QCM-D Monitoring of the Adsorption–Desorption of Expansin on Lignin

“…Overall, BsEXLX1 exhibited a high binding ability on lignin with the maximum adsorption of 260−283 ng cm −2 , which is much higher than that on cellulose (120−160 ng cm −2 ) as measured in our previous study. 18,19 During the experiment, ΔD showed an opposite tendency with the frequency, i.e., it increased to a maximum value before decreasing. In the initial stage, the dissipation value increased rapidly due to the adsorption of BsEXLX1, making the film more viscoelastic.…”

“…Considering the binding ability of expansin, an understanding of the expansin adsorption will greatly contribute to the understanding of the action mechanism. Current research on expansin adsorption mainly concentrates on the adsorption site, adsorbed amount after equilibrium, and real-time adsorption behavior on cellulose. ,− For example, we recently found that cellobiose and xylose can improve the adsorption of Bs EXLX1 on cellulose at low concentrations but disrupt adsorption at high concentrations . However, the adsorption of expansin on lignin is unknown and remains one of the important unanswered questions in the field.…”

“…13,17−19 on cellulose at low concentrations but disrupt adsorption at high concentrations. 19 However, the adsorption of expansin on lignin is unknown and remains one of the important unanswered questions in the field.…”