Study On The Immobilization Of Enzymes With Layer Material--Layered Double Hydroxides

The immobilizations of penicillin G acylase (PGA) and lipase usingcovalent method on the anion layer material-layered double hydroxides(LDHs) have been studied. LDHs are intercalated by glutamic acid and activated by glutaraldehyde before being used as the carrier of the immobilized enzymes. The effects of the quantity of glutamic acid and electrical density of the layered sheet on immobilized enzymes activities are discussed.Some factors influencing the immobilization of PGA are considered. Using 4mL 2.5% (v/v) glutaradehyde solution to activate 0.5g carrier, then immobilizing 4mL PGA on LDHs at temperature of 28 ℃ and pH value of 6.0 for 24h. Under this optimal condition, the activity and the activity retention of the immobilized PGA are 580U/g and 56%, respectively. The operational stability of the immobilized PGA is also discussed.The optimal conditions of lipase immobilization are activating 0.5g carrier with 0.5% (v/v) gultaradehyde solution and immobilizing 12~20mL lipase solution at the temperature of 25-30 ℃ for 20~24h. The activity of the immobilized lipase is about 470U/g and the activity retention is not less than 23%. Comparing with the free lipase, the stability of the immobilized lipase has increased. The hydrolysis of olive oil by immobilized lipase is also studied. The immobilized lipase can hydrolyze olive oil completely in 0.lmol/L phosphatebuffer at the temperature of 45 and pHS.O for 12h. No inhibition is found as the substrate concentration increased up to 56%(v/v). After 10 cycles batch hydrolysis, the hydrolytic rate of olive oil decreased from 93.3% to 75.2%. At last, trying to hydrolyzing olive oil in organic solvent, while founding that immobilized lipase activity in aqueous solution is higher than that of in organic solvent.