An ionic liquid (IL) 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) was employed as a pretreatment agent to improve the hydrolysis efficiency of wool with protease. The effects of IL treatment on weight loss, alkaline solubility, protein release efficiency and amino acid composition of wool fibers were first studied. Then, the mechanism of this improvement was further analyzed through surface morphology, wetting ability and crystalloid structure of IL-treated wool. The results showed that the [BMIM]Cl pretreatment could improve the hydrolysis efficiency of protease for wool keratin. After this [BMIM]Cl treatment, the weight loss of the wool fiber was improved from 2.68% to 4.47%, and the alkaline solubility was increased to 11.64%. UV spectrum of the hydrolyte solution showed that a faster release of protein hydrolysis products could be obtained after such a [BMIM]Cl treatment. The decrease percent of low-sulfur amino acids and partial high-sulfur amino acids further revealed that the [BMIM]Cl treatment had a great effect on the wool hydrolysis with protease. SEM, contact angle and WAXD results showed that the [BMIM]Cl treatment changed the outer and inner structures of wool. The scale surface of wool was damaged to some extent, causing the improvement of wetting ability and decrease of crystallinity. All these changes improved the accessibility of proteases to wool fibers, which was helpful for the improvement of enzymatic hydrolysis efficiency.

Key words: wool, ionic liquid, protease, weight loss, amino acid analysis, enzymatic hydrolysis