Design and Engineering of an Efficient Peroxidase Using Myoglobin for Dye Decolorization and Lignin Bioconversion.

Wen-Jie Guo,Jia-Kun Xu,Sheng-Tao Wu,Xiangshi Tan,Ge-Bo Wen,Ying-Wu Lin,Shu-Qin Gao

doi:10.3390/ijms23010413

Abstract

The treatment of environmental pollutants such as synthetic dyes and lignin has received much attention, especially for biotechnological treatments using both native and artificial metalloenzymes. In this study, we designed and engineered an efficient peroxidase using the O2 carrier myoglobin (Mb) as a protein scaffold by four mutations (F43Y/T67R/P88W/F138W), which combines the key structural features of natural peroxidases such as the presence of a conserved His-Arg pair and Tyr/Trp residues close to the heme active center. Kinetic studies revealed that the quadruple mutant exhibits considerably enhanced peroxidase activity, with the catalytic efficiency (kcat/Km) comparable to that of the most efficient natural enzyme, horseradish peroxidase (HRP). Moreover, the designed enzyme can effectively decolorize a variety of synthetic organic dyes and catalyze the bioconversion of lignin, such as Kraft lignin and a model compound, guaiacylglycerol-β-guaiacyl ether (GGE). As analyzed by HPLC and ESI-MS, we identified several bioconversion products of GGE, as produced via bond cleavage followed by dimerization or trimerization, which illustrates the mechanism for lignin bioconversion. This study indicates that the designed enzyme could be exploited for the decolorization of textile wastewater contaminated with various dyes, as well as for the bioconversion of lignin to produce more value-added products.

Highlights

In the last decade, the environmental pollution caused by organic chemicals has received much attention
The quadruple mutant YRW2 Mb was expressed and purified using the same procedure as that for WT Mb [35], which was further confirmed by ESI-MS analysis (Figure S1)
We evaluated the peroxidase activity of the quadruple mutant YRW2 Mb and the triple mutant YW2 Mb, using both guaiacol and ABTS as the typical substrates under the steady-state conditions at a concentration of 20 mM H2 O2

Summary

Introduction

The environmental pollution caused by organic chemicals has received much attention. The main sources of organic matter in wastewater are synthetic dyes from the textile industry [1] and lignin from the paper industry [2]. Various dyes such as anthraquinones, azo, and triphenylmethane compounds in wastewater threaten aquatic organisms and human health [3]. It is important to effectively degrade organic dyes and utilize lignin in wastewater for environmental treatment. Chemical methods are most used to purify or degrade synthetic dyes and lignin in polluted water. The main degradation methods include physical processes such as membrane filtration, precipitation, flotation, adsorption, and ion exchange, and chemical processes such as electrolysis and chemical reduction/oxidation [5]. Due to its complex structure, amorphous and non-uniform nature, the degradation of lignin generally

Methods

Results

Conclusion