Efficient degradation of Malachite Green by Aeromonas sp. strain DH-6

Microbial decolorization has been investigated extensively. Various microbes have been studied for their dye removing capability; however, microbial decolorizer with a strong environmental adaptability and wide substrate spectrum is of great potential for its possible practical application. Therefore, in this study, Aeromonas  sp. DH-6, a wide dye spectrum decolorizer, was investigated in terms of its use for Malachite Green (MG) remediation. Results indicated that most of carbon sources have no effect on decolorization, while the nitrogen sources of beef extract and yeast extract could enhance MG decolorization significantly. Among the tested metal ions, Cu 2+ , Fe 2+ , and Zn 2+  could significantly inhibit decolorization. Moreover, the strain showed a very stable and efficient decolorization performance in the pH of 5.0-10.0 and at 20-40 o C. Besides, it could almost completely decolorize MG at concentrations ≤ 1000 mg/L within 36 h. Based on UV-visible, GC-MS, and FTIR analysis, biodegradation of MG by the strain DH-6 was confirmed and data showed that MG was decomposed into 4-(Dimethylamino)benzophenone and other metabolites containing –C=O, –NH, and –OH groups. Enzyme analysis showed that tyrosinase, laccase, LiP, NADH-DCIP reductase, and MG reductase might be involved in MG degradation by the strain DH-6. Overall, the results demonstrated that the strain DH-6 will have an effective use as an alternative in MG bioremediation.