Stability and catalytic properties of lipase immobilized on chitosan encapsulated magnetic nanoparticles cross-linked with genipin and glutaraldehyde

BACKGROUND Among many cross-linkers for enzyme immobilization, genipin (Gen) and glutaraldehyde (Glu) as cross-linkers have been commonly investigated to improve the catalytic performance of enzyme immobilized on chitosan encapsulated magnetic nanoparticles (CMNPs). In this work, we compared the stability and catalytic properties of lipase Candida rugosa (CRL) immobilized on CMNPs cross-linked with Gen and Glu, respectively. The CMNPs were first characterized by TEM, XRD and FT-IR. Moreover, some crucial parameters affecting catalytic performances were optimized for Gen-CMNPs-CRL and Glu-CMNPs-CRL preparation. RESULTS The Gen-CMNPs-CRL showed maximum activity at pH 8.0 and 40°C, and retained more than 95% of its initial activity after 7 days storage at 25°C. After 5 cycles re-usage, Gen-CMNPs-CRL still retained over 80% of its initial activity, while Glu-CMNPs-CRL retained only 26% of its initial activity. Kinetic studies confirmed that Gen-CMNPs-CRL and Glu-CMNPs-CRL presented higher substrate affinity characteristics (Km) than free CRL. FT-IR analysis showed that the variance of β-sheet element in the secondary structure of CRL might contribute to the stability and activity enhancement of Gen-CMNPs-CRL. CONCLUSIONS Gen-CMNPs-CRL showed higher pH, temperature, storage and operational stabilities than Glu-CMNPs-CRL. Thus, genepin is a better promising cross-linker than glutaraldehyde for lipase immobilization on CMNPs. © 2015 Society of Chemical Industry