Enhancement on the microbial extracellular electron transfers by modified lignin materials: Application on decolorization of azo dye

Rong-Ping Chen,Jia-Li Cai,Qing Li,Lei Yu,Xin-Yuan Wei,Cheng-Hao Gan,Ru-Xue Liu,Qiang Yong

doi:10.1016/j.jmrt.2021.10.114

Abstract

In the process of biodegradation of azo dye, redox mediators (RMs) were found to significantly enhance the removal efficiency. In this work, biodegradable RMs deriving from lignin-based monomers were prepared via peroxidation to investigate whether similar chemicals present in lignin-rich streams from biorefineries could be used for biological treatment of azo dyes. The as-prepared RMs were characterized by fourier transform infrared spectroscopy (FTIR), gas chromatography-mass spectrometer (GC–MS), cyclic voltammetry and electron paramagnetic resonance, and the degradation metabolites were analyzed by high performance liquid chromatography (HPLC). The induction of RMs accelerated the extracellular electron transfer, resulting efficient methyl orange (MO) decolorization. The decolorization efficiency of MO motivated by the products of vanillin peroxidation were increased from 20% to 95% in 12 h. Moreover, the products deriving from syringaldehyde peroxidation increased the efficiency from 40% to 85% in 24 h. The degradation results of the two RMs were well fitted by zero-order and first-order kinetic models. Under saline condition, the strain still remained a high and stable removal efficiency to MO in the presence of RMs, making it acceptable to be applied in the practical wastewater. The extracellular electron transfers and metabolic products were explored to unveil the mechanisms of enhancement. This study could provide a new route for the functional utilization of lignin-resource and a theoretical guidance for efficient biodegradation of azo dye wastewater.

Highlights

Extracellular electron transfers (EETs) are mainly involved in anaerobic respiration of quinone-respiring strains, which is applicable in many fields, such as microbiological fuel cell, bio-hydrogen production, anoxic denitrification, and bio-reduction of azo dyes
EETs have many applications, including microbiological fuel cell, bio-hydrogen production, reduction and detoxification of heavy metals, anoxic denitrification, and bio-reduction of azo dyes [5,6,7,8,9]. This kind of instinctive function of microbes was nonspecific and low efficient, which needed to be improved by addition of exogenous redox mediators (RMs) [10,11,12]
The products purchased from Sinopharm Chemical Reagent include: Methyl orange, sucrose, (NH4)2SO4, MgSO4·7H2O, Na2HPO4·12H2O, KH2PO4, NaCl, KCl, poly, N-Methyl-2-pyrrolidinone, acetylene black, vanillic acid, malic acid, 4-hydroxybenzoic acid, cinnamic acid, dihydroxybenzophenone

Summary

Introduction

Extracellular electron transfers (EETs) are mainly involved in anaerobic respiration of quinone-respiring strains, which is applicable in many fields, such as microbiological fuel cell, bio-hydrogen production, anoxic denitrification, and bio-reduction of azo dyes. This kind of instinctive function of microbes was nonspecific and low efficient, which needed to be improved by addition of exogenous redox mediators (RMs). Vanillin, syringaldehyde and p-hydroxybenzaldehyde, as the precursors of lignin, were functionally modified to RMs in effort to accelerate the bio-reduction azo dyes

Methods

Results

Conclusion