Mechanisms of anthraquinone dye Vat Blue 4 biodegradation by Pseudomonas aeruginosa WYT and genotoxicity assessment of its transformation products.

[Display omitted] • Pa WYT demonstrated the biodegradation capacity on refractory anthraquinone dyes. • Piperazine between the 9,10-anthraquinone chromophores were cleaved. • DNA damage possibly was mediated by the redox cycle of VB4 dye intermediates. • Total genotoxicity decreases correlated with the quantity of unsubstituted dyes. Dye biodegradation products may cause genotoxicity, raising concerns about the safety of bioremediated water. The underlying biotransformation mechanism and related genotoxicity during anthraquinone degradation remain unclear. In this study, we employed Pseudomonas aeruginosa WYT (Pa WYT) to investigate the biotransformation of Vat Blue 4 (VB4), a dye with a typical anthraquinone structure and low bioavailability. The genotoxicity of the resulting degradation products was also assessed. Novel mechanisms for VB4 biotransformation were identified, including piperazine cleavage, chromophore loss, and the formation of smaller molecular products. A real-time genotoxicity assay showed that VB4 induced oxidative and general stresses to microorganisms, while the total genotoxicity across five stress categories (oxidative, protein, membrane, DNA, and general stresses) gradually decreased as the dye degradation progressed. Overall, capturing and understanding the toxicity dynamics during VB4 bioremediation supports the reliability of this biodegradation method and its potential for treating VB4-contaminated wastewater. [ABSTRACT FROM AUTHOR]