Biodegradation of anthraquinone dyes by Shewanella sp. NTOU1 under anaerobic conditions

Shewanella sp. NTOU1 was able to decolorize a range of anthraquinone dyes [Reactive Blue 4 (RB4), Reactive Blue 19 (RB19), Mordant Red 11 (MR11), Disperse Red 15 (DR15), and Disperse Blue 3 (DB3)] under anaerobic conditions. By supplementing the medium with formate and ferric citrate as the electron donor and acceptor, respectively and cultivating it under the optimum pH (8–9) and temperature (45°C), this strain could decolorize these dyes (1,000 mg/L) at the initial color removal rates of 15–126 mg/L/h and the rates among them were RB19 > RB4 > DB3 > DR15 > MR11. The extent of color removal was in the range of 90–98% for RB19, 86–96% for RB4, 39–41% for MR11, 69–82% for DR15, and 89–91% for DB3. Based on the decolorization products detected by means of GC/MS analyses, probable pathways for the decolorization of these dyes by this strain were proposed.