Effects of Ionic Liquid 1‑Ethyl-3-Methylimidazolium Diethylphosphate on Cellulase Produced by Paenibacillus sp. LLZ1

Ionic liquid (IL) has attracted wide attention as a pretreating solvent for efficient utilization of lignocellulosic biomass. However, IL is known to severely inactivate the cellulases. In this study, the relative activity of Paenibacillus sp. LLZ1 cellulases (PCs) was analyzed in the presence of 1-ethyl-3-methyl­imidazolium diethyl­phosphate ([Emim]­DEP) with respect to carboxy­methyl­cellulose (CMC), filter paper (FP), and microcrystalline cellulose (MCC). With increasing [Emim]­DEP concentration, PCs were differentially inhibited depending on the substrate. Subsequently, the kinetic parameters K m and V max were analyzed. A significant increase in the K m indicated that [Emim]­DEP exerted a negative impact on the affinity of the enzyme on the substrate MCC. Comparatively, the V max was influenced only slightly. Further study on the relative MCCase activity with different substrate content showed that PCs were less inhibited at higher substrate concentration. Finally, sodium dodecyl sulfate polyacrylamide gel electrophoresis demonstrated that the inactivation of endoglucanases was reversible at low [Emim]­DEP concentration (less than 30%) and the irreversibility was onset at high [Emim]­DEP concentration (greater than 40%). The varied effects of [Emim]­DEP were observed in different endoglucanases.