BPA biodegradation driven by isolated strain SQ-2 and its metabolism mechanism elucidation

Bisphenol A (BPA), as an endocrine disruptor, has threatened ecological security. Efficient and low-cost degradation approaches are urgently required in recent years. Biodegradation is a promising alternative technology. Therefore, screening efficient degrading bacteria with BPA as sole carbon source is a research hotspot. In addition, the mechanism of BPA biodegradation needs to be further supplemented. Accordingly, a strain SQ-2 with BPA degradation ability was isolated and identified as Proteus mirabilis in this study. SQ-2 could degrade 1 mg L−1 and 20 mg L−1 BPA by 98.22% and 66.77% within 72 h. Moreover, SQ-2 showed equivalent degradation performance in river water as in minimal salt medium. Furthermore, both the genome and the bacterial metabolites were analyzed to elucidate the degradation mechanism. Results indicated that BPA presented both carbon source and oxidative stress properties. Therefore, SQ-2 secreted antioxidants to sustain its metabolism. Meanwhile, SQ-2 secreted oxidoreductases, hydrolases through Sec-SRP, Tat and type VI secretion pathway to degrade BPA. Three degradation pathways were proposed. The degraded products finally entered the tricarboxylic acid cycle and were further oxidized into carbon dioxide and water. This study enriched the mechanism of BPA biodegradation and might provide new enlightenment for the biodegradation of BPA.