Effect of Ionic Liquids Pretreatment on the Extrraction of Collagen from Calf Skin

Abstract

The use of ionic liquids (ILs) for collagen extraction should be premised of not destroying the triple helix structure of collagen. Herein, the effects of pretreatments by two imidazolium based ILs with different anions, 1-ethyl-methylimidazolium dicyanamide ([EMIM][N(CN)2]) and 1 ethyl-methylimidazolium tetrafluoroborate ([EMIM][BF4]), on the extraction of collagen from calf skins were studied. The dependences of ILs pretreatments on ILs species and concentrations (30%, 50%, and 70% (w/w)) were examined, in terms of the fiber morphology of skins as well as the extraction rate, structural integrity, thermal stability, and aggregation behaviors of collagens. The results of histological analysis and scanning electron microscopy showed that the skin fibers were effectively loosened by the ILs pretreatments. The extraction rate of collagen was improved as the increase of ILs concentration and polarity with the highest value of 28.79%. Moreover, sodium dodecyl sulphatepolyacrylamide gel electrophoresis and Fourier transform infrared spectroscopy confirmed that the structural integrity of collagen was maintained after ILs pretreatments, although the thermal stability of collagen was determined to be slightly decreased by ultra-sensitive differential scanning calorimeter. Finally, pyrene f luorescence analysis and atomic force microscope indicated that the aggregation behavior of collagen was weakened when increasing the ILs concentration and polarity. The green ILs pretreatment of calf skins might be used as an effective approach for the extraction of bioactive collagen with improved yield and purity.