Anaerobic biodecolorization mechanism of methyl orange by Shewanella oneidensis MR-1

Abstract

In this work, we investigated the anaerobic decolorization of methyl orange (MO), a typical azo dye, by Shewanella oneidensis MR-1, which can use various organic and inorganic substances as its electron acceptor in natural and engineered environments. S. oneidensis MR-1 was found to be able to obtain energy for growth through anaerobic respiration accompanied with dissimilatory azo-reduction of MO. Chemical analysis shows that MO reduction occurred via the cleavage of azo bond. Block of Mtr respiratory pathway, a transmembrane electron transport chain, resulted in a reduction of decolorization rate by 80%, compared to the wild type. Knockout of cymA resulted in a substantial loss of its azo-reduction ability, indicating that CymA is a key c-type cytochrome in the electron transfer chain to MO. Thus, the MtrA-MtrB-MtrC respiratory pathway is proposed to be mainly responsible for the anaerobic decolorization of azo dyes such as MO by S. oneidensis.

Evaluation of integrated anaerobic–aerobic biofilm reactor for degradation of azo dye methyl orange

“…Since the boiling point of 4-aminobenzenesulfonic acid exceeded the temperature limit of the GC-MS, only N,N-dimethyl-p-phenylenediamine was detected in the GC chromatogram. From the MS analysis, the main fragmentation ions (m/z) were 136, 121, 105, 93, 77, 60, 40 and 18 which were comparable with other researchers in the N,N-dimethyl p-phenylenediamine determination (Parshetti et al, 2010;Cai et al, 2012;Chen et al, 2008).…”

“…The initial stage of degradation proposed to be the azo bond cleavage which caused the disappearance of absorbance peak at 460 nm with respect to time. Symmetric cleavage of this azo bond tends to the formation of the N,N-dimethyl p-phenylenediamine and 4-amino sulfonic acid (Parshetti et al, 2010;Cai et al, 2012). The N,N-dimethyl p-phenylenediamine was obtained from GC-MS analysis at the retention time 13.395 min.…”

Decolorization by Caldicellulosiruptor saccharolyticus with dissolved hydrogen under extreme thermophilic conditions

“…The decolorization ability of C. saccharolyticus observed in this study is comparable to that of Shewanella oneidensis MR-1 [10] and Pseudomonas luteola [26], which had strong ability of decolorization in previous researches. MO (100 mg/L) was removed completely in $7 h by S. oneidensis MR-1.…”

“…The results of earlier studies suggested the reduced flavins generated by flavin reductases are responsible for the unspecific reduction of azo dyes [7]. And a recent study suggested the electron transport chain of MtrAMtrB-MtrC might be a major avenue for delivering electrons from the outer membrane surface to the azo dyes [10]. There is no report, however, on how the hydrogenase is involved specifically in the dye decolorization process [8].…”

Reductive Decolorization of Azo Dye by Bacteria

“…The multi haem cytochromes MtrF, OmcA, and OmcB may fulfill a function as terminal dye reductase. Furthermore, azo dye decolorization studies have been carried out with MR-1 gene knock-out mutant strains by Yu's group in details recently (Cai et al 2012;Cao et al 2013). It was found that the block of the Mtr pathway resulted in 80 % decrease of the decolorization rate.…”