Effects of electron donors and acceptors on anaerobic reduction of azo dyes by Shewanella decolorationis S12

Abstract

Shewanella decolorationis S12 was able to reduce various azo dyes in a defined medium with formate, lactate, and pyruvate or H(2) as electron donors under anaerobic conditions. Purified membranous, periplasmic, and cytoplasmic fractions from strain S12 analyzed, respectively, only membranous fraction was capable of reducing azo dye in the presence of electron donor, indicating that the enzyme system for anaerobic azoreduction was located on cellular membrane. Respiratory inhibitor Cu(2+), dicumarol, stigmatellin, and metyrapone inhibited anaerobic azoreduction by purified membrane fraction, suggesting that the bacterial anaerobic azoreduction by strain S12 was a biochemical process that oxidizes the electron donors and transfers the electrons to the acceptors through a multicompound system related to electron transport chain. Dehydrogenases, cytochromes, and menaquinones were essential electron transport components for the azoreduction. The electron transport process for azoreduction was almost fully inhibited by O(2), 6 mM of NO3-, and 0.9 mM of NO2-, but not by 10 mM of Fe(3+). The inhibition may be a result from the competition for electrons from electron donors. These findings impact on the understanding of the mechanism of bacterial anaerobic azoreduction and have implication for improving treatment methods of wastewater contaminated by azo dyes.

Azo dye decolorization by halophilic and halotolerant microorganisms

“…Then, another experiment was designed with the usage of purified membranous, periplasmic, and cytoplasmic fractions from S. decolorationis S12 to decolorize azo dyes (Hong et al 2007b). They realised that only the membranous fraction was capable of reducing azo dye in the presence of an electron donor, indicating that the enzyme system for anaerobic azoreduction was located on cellular membrane.…”

Bacterial diversity and composition in major fresh produce growing soils affected by physiochemical properties and geographic locations

“…Most of the anaerobic reduction processes are location specific but can take place both in cytoplasmic and membrane fractions isolated from bacterial cells (Kudlich et al, 1997). However, an essential component required for electron transport from electron donors to azo compounds is thought to be located in membrane fractions from bacterial cell extracts (Hong et al, 2007a(Hong et al, , 2009). This implies that the coupling of oxidation of electron donor and reduction of azo dyes is a universal biochemical phenomenon for azo dyes degradation.…”

“…Likewise, Elbanna et al (2010) reported a complete mineralization of Reactive Lanasol Black B (RLB), Eriochrome Red B (RN) and 1,2 Metal Complexes I Yellow in anaerobic-aerobic sequential system using a consortium of Lactobacillus casei, Lactobacillus paracasei and Lactobacillus rhamnosus. Single strains can also perform the sequential process, but may be less efficient, leading to partial degradation of azo dyes (Hong et al, 2007a). In one such study, Hong et al (2007a) used the bacterial strain Shewanella decolorationis S12, which completely decolorized the Amaranth dye under anaerobic conditions, but when it was exposed to aerobic conditions, the byproducts of amaranth (1-aminenaphthylene-4-sulfonic acid and 1-aminenaphthylene-2-hydroxy-3,6-disulfonic acid) were only partially mineralized.…”

“…Single strains can also perform the sequential process, but may be less efficient, leading to partial degradation of azo dyes (Hong et al, 2007a). In one such study, Hong et al (2007a) used the bacterial strain Shewanella decolorationis S12, which completely decolorized the Amaranth dye under anaerobic conditions, but when it was exposed to aerobic conditions, the byproducts of amaranth (1-aminenaphthylene-4-sulfonic acid and 1-aminenaphthylene-2-hydroxy-3,6-disulfonic acid) were only partially mineralized. The 1-aminenaphthylene-2-hydroxy-3,6-disulfonic acid was completely removed while another component, 1-aminenaphthylene-4-sulfonic acid, was not affected when the cells were exposed to aerobic conditions.…”

Decolorization of Orange I under alkaline and anaerobic conditions by a newly isolated humus-reducing bacterium, Planococcus sp. MC01

“…Stimulation of dye decolorization by the aid of redox mediators has also been reported by other researchers. Hong et al (2007c) revealed that the DE (%) of 1.0 mmol l À1 amaranth degraded by S. decolorationis S12 (20.0 mmol l À1 formate as electron donor) was increased by about 21% with the addition of 5.0 mmol l À1 or 10.0 mmol l À1 Fe(III)-citrate. Hong et al (2007b) also reported that low concentration of anthraquinone-2-sulfonate (AQS) (about 1.0e3.0 mmol l À1 ) accelerated the decolorization of azo dye by strain S12.…”