Synergistic UV and acridine orange mutagenesis enhances polyethylene biodegradation by Sphingobacterium prati BS2

Polyethylene (PE) pollution persists due to its extreme environmental recalcitrance. Microbial degradation offers a promising solution, yet its efficiency in wild-type strains remains limited. To enhance the PE-degrading capability of Sphingobacterium prati BS2, this study applied physical (UV irradiation and microwave) and chemical (acridine orange (AO) and hydroxylamine hydrochloride) mutagenesis, followed by directed screening using PE as the sole carbon source. Among the obtained mutants, the UV-AO combined mutant BS2-UA, showing a clear synergistic effect, exhibited the highest positive mutation rate (23.70%) and maintained high stability across successive generations. BS2-UA displayed improved growth performance and biofilm formation, accompanied by pronounced and sustained culture acidification, as well as superior PE degradation, achieving a weight loss of ∼10% over 50 days, which was approximately 50% higher than that of the wild-type strain. Scanning electron microscopy revealed pronounced surface cracks, while Fourier-transform infrared spectroscopy indicated elevated hydroxyl and carbonyl groups, confirming oxidative modification of PE. These findings demonstrate that synergistic mutagenesis is a potent strategy for enhancing the intrinsic plastic-degrading potential of under-explored bacterial genera like Sphingobacterium, providing high-performance candidates and insights into systems-level traits underlying effective PE biodegradation.