Preparation and characterization of κ-carrageenase immobilized onto magnetic iron oxide nanoparticles

Anfeng Xiao,Caiyun Xu,Yanbing Zhu,Hui Ni,Huinong Cai,Yan Lin

doi:10.1016/j.ejbt.2015.10.001

Abstract

Background: Carboxyl-functionalized magnetic nanoparticles were synthesized via chemical co-precipitation method and modified with oleic acid which was oxidized by potassium permanganate, and κ-carrageenase from Pseudoalteromonas sp. ASY5 was subsequently immobilized onto them. The immobilization conditions were further optimized, and the characterizations of the immobilized κ-carrageenase were investigated. Results: The κ-carrageenase was immobilized onto magnetic iron oxide nanoparticles, and the bonding was verified by Fourier transform infrared spectroscopy. The optimal conditions for κ-carrageenase immobilization were 2.5% (w/v) glutaraldehyde, 13.9 U κ-carrageenase for 20 mg of magnetic nanoparticles, a 2-h cross-linking time, and a 2-h immobilization time at 25°C. Under these conditions, the activity of the immobilized enzyme and the enzyme recovery rate were 326.0 U · g - 1 carriers and 46.9%, respectively. The properties of the immobilized κ-carrageenase were compared with those of the free enzyme. The optimum temperatures of the free and immobilized κ-carrageenase were 60 and 55°C, respectively, and the optimum pH of κ-carrageenase did not change before and after immobilization (pH 7.5). After immobilization, κ-carrageenase exhibited lower thermal stability and improved pH stability, as well as better storage stability. The immobilized κ-carrageenase maintained 43.5% of the original activity after being used 4 times. The kinetic constant value (Km) of κ-carrageenase indicates that the immobilized enzyme had a lower binding affinity for the substrate. Conclusions: Under optimal conditions, the activity of the immobilized enzyme and enzyme recovery rate were 326.0 U · g - 1 ·κ-carrageenase-CMNPs and 46.9%, respectively. The thermal, pH, and storage stabilities of κ-carrageenase-CMNPs were relatively higher than those of free κ-carrageenase.

Highlights

Carrageenans are gel-forming, linear, and sulfated galactans extracted from certain marine red algae and consist of D-galactose residues with alternating α-1,3 and β-1,4 linkages [1]
Carboxyl-functionalized magnetic nanoparticles were synthesized via chemical co-precipitation method, and κ-carrageenase was subsequently immobilized onto carboxyl-functioned magnetic iron oxide nanoparticles (CMNPs)
Peak around 1100 cm-1 on the κ-carrageenase-CMNPs and κ-carrageenase were due to the stretching of C–N from peptide bond in protein

Summary

Introduction

Carrageenans are gel-forming, linear, and sulfated galactans extracted from certain marine red algae and consist of D-galactose residues with alternating α-1,3 and β-1,4 linkages [1]. Carboxyl-functionalized magnetic nanoparticles were synthesized via chemical co-precipitation method, and κ-carrageenase was subsequently immobilized onto carboxyl-functioned magnetic iron oxide nanoparticles (CMNPs). The optimal conditions for κ-carrageenase immobilization were 2.5% (w/v) glutaraldehyde, 13.9 U κ-carrageenase for 20 mg of magnetic nanoparticles, a 2-h cross-linking time, and a 2-h immobilization time at 25°C. Under these conditions, the activity of the immobilized enzyme and the enzyme recovery rate were 326.0 U · g-1 carriers and 46.9%, respectively. Conclusions: Under optimal conditions, the activity of the immobilized enzyme and enzyme recovery rate were 326.0 U · g-1·κ-carrageenase-CMNPs and 46.9%, respectively. The thermal, pH, and storage stabilities of κ-carrageenase-CMNPs were relatively higher than those of free κ-carrageenase

Methods

Results

Conclusion