Aerobic biodegradation of untreated polyester-polyether urethanes by newly isolated yeast strains Exophilia sp. NS-7 and Rhodotorula sp. NS-12

In this study, two polyester-polyether urethane degrading yeasts were isolated from forest soil and wastewater. These isolates were identified through ITS region gene sequencing as two new strains of Exophilia sp. NS-7 and Rhodotorula sp. NS-12. The polyurethanes (PUs) biodegradation ability of two strains was evaluated by urease, protease, esterase, and Impranil® degradation activity assays, Fourier transformed infra-red spectroscopy (FT-IR), scanning electron microscopy (SEM), Sturm test, and Proton nuclear magnetic resonance (H-NMR) spectroscopy. The results showed that Exophilia sp. NS-7 is esterase, protease, and urease positive, and Rhodotorula sp. NS-12 can produce esterase and urease. Both strains can degrade Impranil® as the sole source of carbon with the highest growth rate in 4–6 and 8–12 days, respectively. SEM micrograph revealed PU degradation ability in both strains by showing so many pits and holes in treated films. The Sturm test showed that these two isolates can mineralize PU to CO 2 , and significant decreases in N-H stretching, C-H stretching, C = O stretching, and N-H/ C = O bending absorption in the molecular structure of PU were revealed by the FT-IR spectrum. The detection of new signals in the H-NMR spectrum after the treatment also confirmed the destructive effects of both strains on PU films.