Polyurethane Degrading Bacteria Isolated from Decayed Teak Wood (Tectona grandis Linn. f.)

Polyurethane is a class of polymers characterized by their substantial tensile strength and high melting points which enables them to be extremely durable. Despite its xenobiotic origin, polyure-thane has been found susceptible to biodegradation by microorgan-isms. The main object of this research was to investigate polyurethane degradation by the bacterium isolated from decayed teak wood (Tec-tona grandis Linn. f.). Polyurethane degrading bacteria were isolated using selective medium in the form of LB (Luria Bertani) with the ad-dition of 0.3% Impranil. Bacterial biodegradation activities shown by the changes of polyurethane structure analyzed by FT-IR spectrosco-py. The bacterial identification was carried out based on observations on the morphological characteristics of the colonies, cell morphology and sequences of 16S rRNA encoding genes. One of the potential iso-late that successfully isolated was K9, which demonstrates the disap-pearance of the 1735/cm peak of the characteristic function urethane in the FT-IR analysis. Analysis of the 16S rRNA encoding gene showed that the potential isolate having 98% similarity index to Bacillus safen-sis strain FO-36b. The activity shown by the isolate suggests that the bacteria could be a promising agent for polyurethane degradation.

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.

Study of the Degradation of a Polyesther-Polyurethane by TGA and the Logistic Mixture Model

The logistic mixture model was successfully studied previously in the separation of overlapping steps in some polymeric systems by the authors. In the present work, this method is applied to a polyesther-polyurethane degradation under air and inert atmospheres at several heat rates (5, 10, 15, 20 and 25 °C/min) in dynamic TGA. Every logistic component is fitted by reaction order, Johnson-Mehl-Avrami and Sestak-Berggren kinetics equations in order to calculate its kinetic parameters (activation energy, frequency factor and exponents). The reaction order model gives a good fitting and reproduces accurtelly the experimental curves. Johnson-Mehl-Avrami and Sestak- Berggren equations resulted to be not suitables because of the activation energy values obtained.