Abstract: Chitosan-halloysites nanotube (CTS-HNTs) composite microspheres were successfully prepared by crosslinkingadsorption method, and used to immobilize papain. The successful immobilization of papain on CTS-HNTs composite microspheres was confirmed through infrared spectroscopy, scanning electron microscopy, and fluorescent labeling. The microspheres prepared with 2% CTS and 1% HNTs displayed the highest immobilization efficiency for papain. The optimal immobilization conditions were determined as 1 mg/mL and 10 h for papain concentration and immobilization time, respectively. The optimal pH and temperature for the immobilized enzyme were 6.8 and 60 ℃, respectively, while those for the free enzyme were 7.2 and 50 ℃, respectively. After 30 days of storage, the relative activity of the immobilized and free papain was 62% and 27%, respectively. The immobilized enzyme retained 26.26% of the initial activity after fourth repeated use. The immobilized papain had good storage stability and operational stability, enhancing the utility efficiency of the enzyme, cutting down the cost of enzymatic hydrolysis and enhancing the production efficiency.

Key words: chitosan-halloysites, composite microspheres, immobilized enzyme, papain