Bacterial Community Dynamics During Treatment of Anthraquinone Dye in a Hydrolytic Reactor, an Aerobic Biofilm Reactor, and a Combined Hydrolytic–Aerobic Reactor System

Abstract

Synthetic dyes are extensively used in industrial processes but do not degrade easily in the environment. Microbial decomposition is a cost-effective alternative to chemical and physical degradation processes. In the present study, we studied the potential effects of using an aerobic biofilm reactor, a hydrolytic reactor, and a combined aerobic–hydrolytic reactor system for treating the anthraquinone dye Reactive Blue 19 (RB19). Compared with the aerobic and hydrolytic reactors, the combined aerobic–hydrolytic reactor system achieved the highest removal efficiency regarding color and chemical oxygen demand, at 95.6% and 83.7%, respectively. Microbial communities in the reactors were analyzed with denaturing gradient gel electrophoresis based on bacterial 16S rRNA genes. A statistical analysis of the denaturing gradient gel electrophoresis profiles demonstrated that the structure of the RB19-degrading consortium changed between the different reactors. All band sequences recovered were assigned to two phyla, Proteobacteria and Firmicutes. A clone corresponding to a Shewanella strain was assumed to be responsible for the RB19 decomposition. A Thauera-like microorganism that was active in the combined reactor system was suggested to be a key bacterium responsible for intermediates. Results of this study provide a basis for further research on the degradation of anthraquinone dyes.