Degradation and detoxification of azo dyes with recombinant ligninolytic enzymes from Aspergillus sp. with secretory overexpression in Pichia pastoris.

Siqi Liu,Yanshun Kang,Yingtian Xiao,Huan Liu,Xiaolin Xu

doi:10.1098/rsos.200688

Siqi Liu, Yanshun Kang + Show 3 more

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https://doi.org/10.1098/rsos.200688

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Abstract

Ligninolytic enzymes, including laccase (Lac), manganese peroxidase (MnP) and lignin peroxidase (LiP), have attracted much attention in the degradation of contaminants. Genes of Lac (1827 bp), MnP (1134 bp) and LiP (1119 bp) were cloned from Aspergillus sp. TS-A, and the recombinant Lac (69 kDa), MnP (45 kDa) and LiP (35 kDa) were secretory expressed in Pichia pastoris GS115, with enzyme activities of 34, 135.12 and 103.13 U l−1, respectively. Dyes of different structures were treated via the recombinant ligninolytic enzymes under the optimal degradation conditions, and the result showed that the decolourization rate of Lac on Congo red (CR) in 5 s was 45.5%. Fourier-transform infrared spectroscopy, gas chromatography–mass spectrometry analysis and toxicity tests further proved that the ligninolytic enzymes could destroy the dyes, both those with one or more azo bonds, and the degradation products were non-toxic. Moreover, the combined ligninolytic enzymes could degrade CR more completely compared with the individual enzyme. Remarkably, besides azo dyes, ligninolytic enzymes could also degrade triphenylmethane and anthracene dyes. This suggests that ligninolytic enzymes from Aspergillus sp. TS-A have the potential for application in the treatment of contaminants.

Highlights

This article has been edited by the Royal Society of Chemistry, including the commissioning, peer review process and editorial aspects up to the point of acceptance
Dyes of different structures were treated via the recombinant ligninolytic enzymes under the optimal degradation conditions, and the result showed that the decolourization rate of Lac on Congo red (CR) in 5 s was 45.5%
Similar metabolites were obtained in another study from the degradation of CR with Lac from Ganoderma lucidum [30]. These results suggest that azo dyes can be degraded and detoxified by ligninolytic enzymes

Summary

Introduction

This article has been edited by the Royal Society of Chemistry, including the commissioning, peer review process and editorial aspects up to the point of acceptance. Ligninolytic enzymes, including laccase (Lac), manganese peroxidase (MnP) and lignin peroxidase (LiP), have attracted much attention in the degradation of contaminants. Besides azo dyes, ligninolytic enzymes could degrade triphenylmethane and anthracene dyes. Multiple technologies have been introduced to remove azo dyes such as sorption, chemical oxidation, electrochemical degradation and ultrafiltration [4,5,6], but these methods are limited; for example, the physical processes do not destroy the dyes, the chemical processes are non-selective, operational cost is high and toxic by-products are produced [2]. In addition to white-rot fungi [10], Aspergillus [11,12] has been used to remove dyes through absorption by mycelium, degradation with ligninolytic enzymes or a combination of both. The enzymatic treatment has more valuable advantages than the microbial treatment in wastewater remediation

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