(787e) Role of Tween-80 in Reduction of Nonproductive Cellulase Binding to Lignin

A key limitation in the enzymatic hydrolysis of lignocellulose to produce soluble sugars is the nonproductive binding of the enzymes to biomass components such as lignin.  Bulk studies on hydrolysis of cellulosic substrates have suggested that additives enhance both conversion of sugars and enzyme recovery when lignin is present, where nonionic surfactants are the most widely studied additives. However, the specific mechanism underlying the use of surfactants is not well understood.  To study the effect of nonionic surfactant Tween-80 and the interactions with cellulase enzyme on lignin, model lignin thin films are prepared and investigated as a function of the adsorbing solution using a Quartz Crystal Microbalance with Dissipation monitoring (QCM-D).  Model lignin films were synthesized by dissolution of dry lignin powder in ammonium hydroxide solution followed by coating onto a quartz crystal resonator.   The cellulase for this study is a commercially available mixture of enzymes derived from Trichoderma reesei.  In-situ studies of single-component binding show that cellulase is bound to the lignin surface irreversibly, while Tween-80 is partially (but not completely) reversible upon rinsing with buffer. Co-adsorption of Tween-80 and cellulase (where both are introduced together) resulted in an apparent net reduction in the amount of cellulase adsorbed on lignin. Sequential adsorption experiments were carried out by varying the order and concentration of Tween-80 and cellulase introduction to lignin surfaces to explore the possibility for displacement of cellulase or pretreatment of biomass using Tween-80. The results of the sequential adsorption experiments suggest that Tween-80 was able to displace adsorbed cellulases, but quantifying the amount of cellulase displaced was difficult with QCM-D as it measures the net change in piezoelectric properties due to mass adsorbed and desorbed on the sensor. Further studies are underway to use analytical methods to quantify the amounts of cellulase desorbed under various conditions and to better understand the mechanism by which the surfactants reduce the nonproductive binding of cellulases through their interaction with lignin.