Studies on One-Pot Enzymatic Depolymerization of Cellulose in Ionic Liquids

Lignocellulosic biomass is a renewable, low cost, non-food and abundant feedstock for biofuel production and a source of C atoms for chemistry alternative to fossil resources. The most important factor hampering massive exploitation of cellulose, the main component of plant biomass, is its well known low reactivity and recalcitrance towards chemical processing. The usual steps in producing biofuels from cellulosic sources are: pre-treatment followed by cellulose precipitation, enzymatic hydrolysis and fermentation. A possible greener alternative for the activation of cellulose fibrilles towards facile hydrolysis and/or derivatization passes through an emerging chemical pre-treatment step using ionic liquids (ILs) [1]. Unlikely, the more common cellulases have been reported to be inactivated by ILs [2]. In this work we describe a single-batch, homogeneous phase enzymatic depolymerization of cellulose catalyzed by a commercial cellulase (EC 3.2.1.4) in the presence of different ILs. We used the industrial enzymatic preparation IndiAge® Super GX Plus (a monocomponent endoglucanase EGIII (Cel12A) from Trichoderma reesei produced by Genencor presently a subsidiary of Dupont). This enzyme already showed exceedingly good performance for the depolymerization of dissolved cellulose in [BMIM][Cl] without the usual pre-treatment, known as dissolution-regeneration of cellulose in its amorphous form [3]. After these promising results, we have extended our screening towards two more friendly ionic liquids such as 1-ethyl-3-methylimidazolium acetate ([EMIM][Ac]) and diethylphosphate ([EMIM][DEP]) and the present study presents a useful comparison of the effect on stability and activity of IndiAge® Super GX Plus in these media which could be amenable of scale-up and innovative industrial applications. _______ [1] Dadi, A.P.; Varanasi, S.; Schall, C.A. Biotechnol. Bioeng., 2006, 95 (5), 904-910. [2] Turner, M.B.; Spear, S.K.; Huddleston, J.G.; Holbrey, J.D.; Rogers, R.D. Green Chem., 2003, 5(4), 443-447. [3] D’Arrigo. P.; Allegretti, C.; Tamborini, S.; Formantici, C.; Galante, Y.; Pollegioni, L.; Mele, A. J. Mol. Cat. B, 2014, 106, 76-80.