Improvement of Laccase Activity Via Covalent Immobilization over Mesoporous Silica Coated Magnetic Multiwalled Carbon Nanotubes for the Discoloration of Synthetic Dyes

Pascal Habimana; Jing Gao; Jean Pierre Mwizerwa; Jean Bernard Ndayambaje; Hengrao Liu; Pengqian Luan; Li Ma; Yanjun Jiang

doi:10.1021/acsomega.0c05081

Improvement of Laccase Activity Via Covalent Immobilization over Mesoporous Silica Coated Magnetic Multiwalled Carbon Nanotubes for the Discoloration of Synthetic Dyes

ACS Omega. 2021 Jan 22;6(4):2777-2789. doi: 10.1021/acsomega.0c05081. eCollection 2021 Feb 2.

Authors

Pascal Habimana¹, Jing Gao¹, Jean Pierre Mwizerwa², Jean Bernard Ndayambaje³, Hengrao Liu¹, Pengqian Luan¹, Li Ma¹, Yanjun Jiang¹

Affiliations

¹ School of Chemical Engineering and Technology, Hebei University of Technology, 8 Guangrong Road, Hongqiao District, Tianjin 300130, China.
² College of Mechatronics and Control Engineering, Shenzhen University, Houhai Ave, Nanshan District, Shenzen, Guangdong Province, 518060, China.
³ University of Rwanda, College of Science and Technology, 3900 Kigali, Rwanda.

Abstract

Due to its environmental friendliness and biodegradable ability, the enzymatic decolorization of azo dyes is the best option. However, the free enzyme suffers from various limitations, including poor stability, no repeatable use, and a high expense, which is the key drawback for its practical use. In this analysis, the laccase enzyme was immobilized in mesoporous silica coated magnetic multiwalled carbon nanotubes (Fe₃O₄-MWCNTs@SiO₂) by a glutaraldehyde cross-linker to create an easily separable and stable enzyme. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) were used to characterize the as-synthesized Fe₃O₄-MWCNTs@SiO₂. Laccase immobilized in Fe₃O₄-MWCNTs@SiO₂ showed a good improvement in temperature, pH, and storage stability. Moreover, the operational stability of the biocatalyst was improved, retaining 87% of its original activity even after 10 cycles of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) oxidation. The biocatalysts were applied for the decolorization of selected azo dyes without a mediator, and up to 99% of Eriochrome Black T (EBT), 98% of Acid Red 88 (AR 88), and 66% of Reactive Black 5 (RB5) were decolorized. Based on these properties, the biocatalysts can be potentially utilized in various environmental and industrial applications.