Degradação biótica do politereftalato de etileno irradiado por ultravioleta com a utilização do fungo ligninolítico Lentinula edodes

Abstract

The polyethylene terephthalate (PET) is a thermoplastic polyester with widespread use of the carbonated beverage industry. This material, when disposed of improperly in the environment like other solid waste becomes an environment burden. It may cause pollution environmments. As well as the proliferation of disease vectors, among others. With respect to the advancement of research in search of alternatives to minimize environmental impacts from the disposal of polymeric materials, emerge as alternatives, the research photo degradative and biological processes to the degradation of these material. The photodegradation processes include ultraviolet radiation, a high energy light which can cause changes include ultraviolet radiation, a high energy light which, can cause change in the polymer structure which causes degradation/destabilization of the material. Furthermore, the use of Basidiomycete fungi responsible for the degradation of natural compounds with large carbon chains applied to decomposition of polymeric material is considered a promising alternative. The Lentinula edodes , popularly known as shiitake is a great commercial interest fungus, in addition to being edible, produces large quantity of hydrolase and oxidade for the conversion of lignocellulosic wastes, in this study, we used PET bottles crystal virgin, pre-consumer, as a substrate for the growth of the fungus L. edodes. The tests proceeded in two stages, abiotica and biotic. In abiotic degradation , phase PET specimens cult from the central strip of the bottle were subjected to ultraviolet radiation in a chamber accelerated UV irradiation. The time periodos were 0h/ without irradiation, 24 hours, 48 hours and 96 hours uninterrupted. The 4groups (0h, 24h, 48h, 96h and) were characterized by thermogravimetric analysis (TG), Analysis of Diferential Scanning Calorimetry (DSC), Infrared Spectroscopy Fourier Transform (0h and 96h) and Mechanical Tensile test (ASTM-D638-10), to analyse the effect of radiation on the physicochemical property of the samples. The second stage of degradation, biotic, consisted of testing interaction between the fungus L. edodes and PET. The treatments used were grown in petri dishes, cultivation in tubes, the semisolid fermentation axenic culture and maintened for different periods of time. The following variables by the gravimetric method gave a weight loss percentage, then the samples were subjected to light microscopy analysis, thermogravimetric analysis, TG/DTG and DSC, and the axenic culture was determined traction mechanical. The results indicate that UV irradiation significantly modifies the properties of PET, a fact that influences the stability and biodegradability. The percentage of average mass loss, obtained in different trials, regardless of the type and the time periods of the treatment were of 0,44% for PET 0h without irradiation the lowest recorded value, 1,28% for PET 24, the highest value recorded and also 1.07% for PET 48h and 0.95% for PET 96h, different UV irradiation phases. Through the photomicrographs, we observed degradation of the material, with the presence of presence of excavations and failures, but it was also observed that the fungus can strongly adhere to the polymer matrix, and procedure for removal was not be affective, a facts that leaves fungus remains inside the PET. Oscilations in thermal and mechanical properties of PET could be observed, another indication that the fungus L. edodes has potential for application in biodegradation process, and UV irradiation acts favorably to this process, finally are made suggestions aimed at improving biodegradation results and more specific knowledge of its processes.