Physiology and biochemistry of reduction of azo compounds by Shewanella strains relevant to electron transport chain

Abstract

Azo dyes are toxic, highly persistent, and ubiquitously distributed in the environments. The large-scale production and application of azo dyes result in serious environmental pollution of water and sediments. Bacterial azo reduction is an important process for removing this group of contaminants. Recent advances in this area of research reveal that azo reduction by Shewanella strains is coupled to the oxidation of electron donors and linked to the electron transport and energy conservation in the cell membrane. Up to date, several key molecular components involved in this reaction have been identified and the primary electron transportation system has been proposed. These new discoveries on the respiration pathways and electron transfer for bacterial azo reduction has potential biotechnological implications in cleaning up contaminated sites.

Azo dye removal in a membrane-free up-flow biocatalyzed electrolysis reactor coupled with an aerobic bio-contact oxidation reactor

“…In comparison, biological reductive methods are attractive, due to less expense and high decolorization efficiency of azo dyes; azo dyes are typically recalcitrant to microbial aerobic oxidation. Anaerobic treatment processes are able to reductively cleave azo linkages and form aromatic amines, which result in decolorization [17]. However, anaerobic reduction processes are usually slow and requires an exogenous electron donor for reducing azo dyes [18,19].…”

Electrochemical reduction of disperse orange 1 textile dye at a boron-doped diamond electrode

“…The largest class of these substances is the azo category, where aromatic moieties are linked together by azo (-N=N-) chromophores, which includes reactive, disperse, and acid textile dyes [2]. The compounds are toxic, highly persistent, and are regarded as environmental pollutants that threaten aquatic life and human health [2,3].…”

DREAM Assay for Studying Microbial Electron Transfer

“…Brigé et al [12] describe the key electron transport components involved in reduction of azo dyes. Microbial azo dye reduction, which was previously attributed to individual enzymes and enzyme systems such as azoreductases and specific dehydrogenases [13], is now understood to be a direct consequence of the respiratory electron transport system of microbes [14].…”