ИСТИНА

Presently, the world is facing the problem of usage and processing of polystyrene. The high stability of this polymer compound has led to its widespread application in the human life and the long duration of natural decomposition, which gives polystyrene the status of xenobiotic. The danger of environmental pollution requires the development of safe and environmentally friendly methods of disposal of polystyrene. In search of a solution, scientists’ attention turned to microbial degradation. The advantages of biotechnological methods are realization of process in moderate conditions: at physiological temperatures, normal pressure and pH of the environment; low output of polluting by-products; low application cost. At the same time, the diversity of enzyme systems and the lability of metabolism determine the ability of microorganisms to degrade a wide range of xenobiotic compounds. At the moment, biodegradation is not fully understood. It is known that the main mechanism involved in biodegradation is the adhesion of microbes to polymers followed by surface colonization. Enzymatic hydrolysis of plastics involves two stages: first, enzymes are attached to the polymer substrate and hydrolytic division occurs. Products of polymers decomposition such as oligomers, dimers and monomers possess low molecular weights and are eventually converted to carbon dioxide and water by mineralization. Under aerobic conditions oxygen is used as an electron acceptor by the bacteria, followed by the synthesis of smaller compounds, thus carbon dioxide and water are produced as the end products. Under anaerobic conditions polymers are destroyed by the microorganisms in the absence of oxygen. Sulfate, nitrate, iron, carbon dioxide and manganese are used by anaerobic bacteria as electron acceptors. New microbial enzymes and pathways need to be explored to optimize conditions under which polymers can be degraded efficiently. The purpose of this study is to explore the possibilities of microbial degradation of polystyrene and its intermediates. It is planned to isolate and describe the microbial communities and individual strains that decompose polystyrene. The experiments will involve both aerobic and anaerobic microorganisms, including specific groups of sulfate and nitrate reducers. Further, the selection of the optimal cultivation conditions will be carried out. Methods of destruction of the polymer chain will be applied such as pretreatment of plastic with ultraviolet light and sonication. The final stage of the study will include investigation of the mechanisms of polystyrene biodegradation at the cellular and molecular level through the analysis of intermediates by gas chromatography, Fourier-transform infrared spectroscopy (FTIR) and mass spectrometry.