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. • Insect symbiotic bacteria have potential application in plastic biodegradation. • Xanthomonas strain from Japanese carpenter bee is effective PU-degradable bacterium. • Xanthomonas strain was able to use polyacryl-based PU as a nutritional source. • Xanthomonas strain was able to degrade other types of PS-PU and PE-PU.