Biodegradation of polyurethane by Japanese carpenter bee gut-associated symbionts Xanthomonas sp. HY-71, and its potential application on bioconversion

Abstract

In this study, we evaluated the effects of the Xanthomonas sp. HY-71 strain isolated from the intestine of a Japanese carpenter bee (Xylocopa appendiculata), on polyurethane (PU) degradation and bioconversion. The abilities of the strain to degrade polyacrylic-, polyester-, and polyether-based PU were characterized by weight loss measurement, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM), and chemical composition analysis. The cell-free filtrates of the strain showed 88.12% of acryl PU-Siegel degradation rates (100 mg/mL) within 3 days. FTIR spectroscopy revealed changes in functional groups, with decreased C=O (1725 cm ？1) and aliphatic chain signals (704 cm ？1) and increased N？H stretching (3314 cm ？1), N？H bending with C？N stretching (1524 cm ？1), C？O？C stretching (1040 cm ？1), and C？N stretching (1226 cm ？1). Polyester-PU and polyether-PU foams, respectively, lost 23.95% and 10.95% of their weight after 2 weeks. SEM revealed surface morphology and structural changes such as holes, cracks, roughness, and grooves. In addition, the bioconversion capability of HY-71 using PU as a nutritional source was also demonstrated by monitoring the exopolysaccharide production yield in the presence of PU foam. The exopolysaccharide yields with acryl PU-Siegel and PS-PU foam (24.6 g/L and 22.6 g/L, respectively) were significantly higher than those of the control and polyether-PU treatments. This study is the first on the insect gut microbe Xanthomonas sp. HY-71 strain, which has PU degradation capability, and provides insight into the potential applications of insect-related bacteria in plastic waste management.