Stabilizing immobilized cellulase by ionic liquids for saccharification of cellulose solutions in 1-butyl-3-methylimidazolium chloride

Abstract

A new approach to improve the cellulase stability against 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]), based on coating of immobilized enzyme particles with hydrophobic ILs, is proposed. The stability of commercial cellulase (Celluclast^®), immobilized onto a polymeric support (Amberlite XAD4), was first studied in ten different ionic liquids (ILs) at 50 and 80 °C. Hydrophobic ILs clearly enhanced the enzyme thermal stability. Butyltrimethyl-ammonium bis(trifluoromethylsulfonyl)imide ([N₁₁₁₄][NTf₂]) enhances half-life time of the immobilized enzyme at 50 °C up to 4 times, while [Bmim][Cl] behaved as a powerful enzyme deactivating agent. Thus, the stability of cellulase in hydrophobic IL/[Bmim][Cl] mixtures was greatly improved with respect to [Bmim][Cl] alone. A stabilized cellulase derivative obtained by coating immobilized enzyme particles with [N₁₁₁₄][NTf₂], has been then successfully used for the saccharification of dissolved cellulose in [Bmim][Cl] (i.e. up to 50% hydrolysis in 24 h) at 50 °C and 1.5 w/v water content.