5-89: Towards the Development of Cellulases compatible with Ionic Liquid Pretreatment for Sachharification of Cellulosic Biomass

Enzymatic hydrolysis is the rate-limiting step in the fermentation of biomass to sugars. The main barrier is the highly crystalline structure of cellulose that limits accessibility to enzyme adsorption sites and slows the hydrolysis of cellulose to sugars in aqueous media. To increase enzyme accessibility, a combination of high temperature and extremes of pH are used during common pretreatment steps like dilute acid or ammonia fiber explosion.  We are exploring the use of Ionic liquids (IL), a new class of environment friendly, non-volatile solvents, in the pretreatment of cellulosic biomass. IL’s have been shown to dissolve cellulose, which can be recovered in the amorphous form by the addition of antisolvents like water. However, significant decreases in cellulase activity in the presence of trace amounts of IL’s have been reported in literature, necessitating extensive processing to remove residual IL’s from the regenerated cellulose. To simplify the entire process, it is necessary to develop cellulases that are stable and active in the presence of trace amounts of IL’s. Towards that goal, we are investigating the stability of extremophilic enzymes, for use with the IL, 1-Ethyl-3-methylimidazolium acetate (EMIM acetate). The endoglucanase from the hyperthermophilic bacterium Thermatoga maritima (Tma cellulase) was purified by affinity chromatography and the enzymatic hydrolysis activity was measured in the presence of varying concentrations of EMIM acetate.  Herein, we show a comparison of the enzymatic efficiency between the commercially available T.viride cellulase from Sigma and the Tma cellulase and the differences related to biochemical properties.