Hydrophobic surface modification of chitosan gels by stearyl for improving the activity of immobilized lipase

The hydrophobic surface modification of chitosan gels was carried out using the amidating reaction of amido groups on a gel surface with stearic acid activated by 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). Lipases from Candida rugosa were adsorbed on the nascent chitosan gels (CS) and stearyl-modified gels (SCS) with different degrees of amidation. The increased surface hydrophobicity of chitosan gels improved the adsorption capacity and activity of the immobilized lipase. SCS with 31.46% amidation showed the maximum activity retention (83.43%). The experimental results suggest that the moderate surface hydrophilicity/hydrophobicity of chitosan gels is necessary for the improvement of the activity of immobilized lipase.