Isolation of an SDBS-degrading Bacterium and Its Toxicity-mitigation Effect on Carassius auratus

To evaluate the ecological risks of surfactant contamination to fish and explore potential bioremediation strategies, a highly efficient sodium dodecylbenzene sulfonate (SDBS)-degrading strain, designated XY-1, was isolated from the environment. Based on physiological and biochemical characteristics as well as 16S rRNA gene sequence analysis, strain XY-1 was identified as Serratia sp. XY-1. The strain was capable of completely degrading 300 mg·L^-1 of SDBS and exhibited high degradation efficiency (>90%) across a broad range of temperatures (15-30 ℃) and pH values (6.0-10.0). Notably, XY-1 exhibited 46.7% degradation at 0 ℃ indicating its ability to function under low-temperature conditions and its broad pH adaptability. Orthogonal experiments indicated that the optimal degradation conditions were pH 7.0, an inoculation dose of 4%, an initial substrate concentration of 550 mg·L^-1, and a culture duration of 24 h. Toxicological assays revealed that the 24 h median lethal concentration (LC₅₀) of SDBS for juvenile goldfish (Carassius auratus) was 569.3 mg·L^-1. Compared with the control group (53.3%), the presence of strain XY-1 significantly reduced the mortality of goldfish under acute SDBS exposure (36.6%, p < 0.05). These findings demonstrate that XY-1 not only possesses strong SDBS-degrading capacity but also effectively mitigates its acute toxicity to aquaculture fish, underscoring its potential importance in safeguarding aquatic environments and the health of cultured species.