Porcine pancreatic lipase (PPL) was chemically modified with various functional ionic liquids (ILs) to increase its catalytic performance in water-miscible IL. Catalytic activity and thermostability were tested with a p-nitrophenyl palmitate (pNPP) hydrolysis reaction. The native enzyme lost 18% of its initial activity in 0.4M IMMIrn][MeSO4], whereas the activities of all the modified enzymes increased. The [HOOCB-MIm][ICI] modification led to a 2-fold increase in activity in 0.3 M [MMIrn][MeSO4] than in aqueous. All the modified enzymes exhibited higher thermostability compared with the native enzyme at high temperature. In particular, the [HOOCBMIm][Cl] modification led to a 6-fold increase in thermostability at 60 degrees C. Conformational changes were confirmed by fluorescence spectroscopy and circular dichroism spectroscopy to elucidate the mechanism of catalytic performance alteration. (C) 2014 Elsevier Ltd. All rights reserved.