Biodecolorization and partial mineralization of Reactive Black 5 by a strain of Rhodopseudomonas palustris

A strain of photosynthetic bacterium, Rhodopseudomonas palustris W1, isolated from a lab-scale anaerobic moving bed biofilm reactor (MBBR) treating textile effluent was demonstrated to decolorize Reactive Black 5 (RB5) efficiently under anaerobic condition. By a series of batch tests, the suitable conditions for RB5 decolorization were obtained, namely, pH <10, light presence, glutamine or lactate as carbon source with concentration more than 500 mg/L when lactate is selected, NH4Cl as a nitrogen source with concentration more than 100 mg/L, NaCl concentration not exceeding 5%, and RB5 concentration less than 700 mg/L. In addition, ultraviolet-visible (UV-Vis) spectrum scan and High Performance Liquid Chromatography/Mass Spectrometry (HPLC-MS) were used to analyze the metabolites of RB5 decolorization of W1. The results showed that partial aromatic amines produced with RB5 reduction were further degraded during the extended period. Anaerobic partial mineralization of RB5 was suggested, and a possible degradation pathway was proposed.