Screening, UV mutagenesis, and exploration of enzymatic degradation mechanisms in the highly efficient polyurethane-degrading Bacillus sp. J-11.

Aims: This research aims to screen and identify a microbial strain capable of efficiently degrading waterborne polyurethane used in the biomedical field. Furthermore, the research seeks to enhance the strain's degradation capability through ultraviolet mutagenesis and elucidate its enzymatic degradation mechanism.

Methods and results: We successfully isolated the target strain from the soil sample and identified it as Bacillus sp. J-11. Under optimized culture conditions (substrate concentration of 0.4%, temperature of 30°C, and pH of 6.0), strain J-11 exhibited remarkable degradation capability towards biomedical-grade polyurethane emulsion (Baymedix® CD104), achieving a degradation efficiency of 78.2% within 4 days. Gel permeation chromatography (GPC) analysis demonstrated a progressive decrease in the molecular weight of the polyurethane film over time. Thermogravimetric analysis (TGA) further revealed a reduction in thermal stability, while extended depth field microscopy (EDFM) uncovered significant microscopic structural changes, including holes and collapse on the film surface. Additional degradation experiments conducted on commercial PU foam under co-carbon conditions showed that strain J-11 achieved a degradation rate of 37.6% within 30 days. Enzyme activity assays indicated that the hydrolytic and oxidative enzymes secreted by strain J-11 played a critical role in the degradation process.

Conclusions: Strain J-11 exhibits highly efficient biodegradation potential through the secretion of hydrolases and oxidases, which break down the molecular chains of polyurethane. This study has elucidated its degradation pathway and provided a theoretical foundation for future mechanistic investigations and the management of biomedical material waste.