Isolation and identification of microorganisms for polyurethane degradation

Plastic wastes decomposition has been a pressing environmental problem worldwide. In this study, polyurethane (PUR), a thermoset plastic was tested for biodegradation by polyurethane-degrading microorganisms that were isolated from a dumpsite at Kamishihoro, Tokachi, Obihiro, Japan. Actinomycetes were the most abundant microorganisms from soil samples. From the 65 isolated microbial species, 16 possessed polyurethane-degrading ability. These isolates exhibited clearing zones on Yeast-extract salts + Agar and gelatin with polyurethane (YES-AG + PUR). The PUR-degrading isolates were characterized and identified based on their DNA sequence patterns. Some isolates belong to the same genus or species. They were Bacillus chitinolyticus (B03, B04, B07), Streptomyces spp. (B13, B19, C13a, C15, C17a, C17b), Pseudomonas sp. (B20), Bacillus pumilus(B21), Streptomyces cuspidosporus (C10b, C18, C19) and Pseudallesscheria baydii (F04, F07). Streptomyces sp. coded as C13a, with base sequence homology of 99.7% with Streptomyces albogriseolus, was believed to produce the highest amount of both exo- and endo polyurethanases. This was demonstrated by the widest clearing zones when broth and cell-bound supernatants were inoculated into the YES-AG + PUR plate.