Improved stability and catalytic activity of graphene oxide/chitosan hybrid beads loaded with porcine liver esterase

ABSTRACT

Graphene oxide/chitosan and reduced graphene oxide/chitosan (GO/CS and RGO/CS) beads were prepared by precipitation with NaOH. Porcine liver esterase was immobilized on these beads to give GO/CS/E and RGO/CS/E beads. The optimum conditions for the maximum activity of RGO/CS/E beads were pH 8 and 50°C. The stability of the enzyme immobilized on GO/CS/E and RGO/CS/E was high in the pH range of 5–8. The GO/CS/E beads showed superior stability compared to that of the free enzyme and CS/E beads between 20 and 50°C. Kinetic analysis showed that GO/CS/E was a better catalyst than the RGO/CS/E beads with a lower K_m value of 0.9 mM. The hybrid beads also retained more than 95% activity after 10 consecutive cycles. The GO/CS/E and RGO/CS/E beads retained 84% and 87% activity after 40 days at 4°C. The GO/CS/E beads were used for the successful hydrolysis of methyl 4-hydroxy benzoate.

KEYWORDS:

• Chitosan
• FT-IR
• graphene oxide
• porcine liver esterase
• reduced graphene oxide
• SEM

Conflict of interest

This manuscript has not been published elsewhere and has not been submitted simultaneously for publication elsewhere.

Additional information

Funding

This work was supported by the Department of Science and Technology, Ministry of Science and Technology [Grant Number SR/S5/GC-13/2005] and Department of Biotechnology, Ministry of Science and Technology, Government of India [Grant Number BT/PR10097/NNT/28/101/2007].