Chemical modification of Purolite A109 for application in lipase immobilization

Abstract

Modern industry recognizes enzymes as important catalysts for batch production of food, drugs and cosmetics. Because of their price and poor technical characteristics in free form, enzymes are mostly used as immobilized derivative. Therefore, there is a constant need for new and improved supports, possessing sufficient amount of active groups on it's surface to interact with enzyme, but on the other side chemically inert to the reaction media. Mechanical stability and price range are as much important as chemical stability. The aim of this study was to investigate properties of modified ionic resin Purolite A109 for lipase immobilization. Purolite A109 is polystyrenic (styrene-divinylbenzene copolymer), macro porous anion exchange resin with primary amine weak base functional groups. It's advantages could be low price, and excellent mechanical and chemical characteristics. Modification of this resin was performed using cyanuric chloride (CTC) and epychlorhydrine. In both cases FTIR spectroscopy confirmed that modification process was successful. Lipase from Candida rugosa was immobilized on both modified supports. Approximately 30% of proteins was bound to both carrier. Hydrolytic activity of both, free and immobilized lipase was determined, and based on these results activity retention after immobilization process was calculated. Results showed that significantly higher activity retention was obtained in case of CTC-Purolite – 67 %. Thermal stabilities of these two immobilized enzymes on 65 °C were compared to thermal stability of free enzyme. Relative activity of free enzyme decreased below 50% of initial activity within 30 min. On the other hand, both immobilized enzymes showed significant thermal stability. Relative activity of epoxy-Purolite dropped below 50 % of initial activity within 3 hours, while CTCPurolite dropped below 50 % of initial activity within 5 hours.