The environmental issue of plastics, especially microplastics, is becoming increasingly more important due to its impact on soil and ecosystems. Plastic breaks down in the environment into smaller particles called microplastics (1 μm to 5 mm), which pose a serious threat to biodiversity and soil health. The main sources of microplastics in soil include mulches, and contaminated sludge and compost. Biodegradable plastics have been developed as an alternative to conventional plastics with the hope of being more environmentally friendly. Biodegradation of microplastics on soil takes place through microbiological processes, where microorganisms such as bacteria and fungi break down plastic into smaller molecules. Microbiological degradation of microplastics includes stages such as biofilm formation, depolymerization, mineralization and biotransformation. Microorganisms, mainly bacteria and fungi, first form a biofilm on the surface of the plastic, which enables efficient decomposition with the help of enzymes. Depolymerization breaks down plastic polymers into smaller molecules, which are then metabolized by microorganisms inside the cells. Mineralization leads to the conversion of these molecules into simple compounds such as CO2 and H2O, while biotransformation occurs when mineralization is incomplete. The final products of decomposition enter natural biochemical cycles. However, various factors such as temperature, humidity and chemical composition of the plastic affect the effectiveness of this process. For now, the complete mineralization of microplastics into CO2 and H2O has not been experimentally confirmed, mainly due to the chemical composition of the material, incomplete microbial metabolic pathways, and variable environmental conditions. Research shows that the rate of biodegradation is directly related to the microorganisms that colonize the surface of the microplastic. Therefore, it is crucial to focus research on long-term field experiments and the development of such materials that degrade efficiently even outside laboratory conditions, with an emphasis on reducing long-term accumulation in the soil.
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