Practically important metabolites of Rhodococcus erythropolis Au-1 strain were obtained: trehalose lipids, exopolysaccharide and cellular polymer – polyhydroxyalkanoate. The structures of the products were established by the methods of TLC, IR and UV-Vis spectroscopy. The purification of trehalose lipids from crude extract was carried out using silica gel column chromatography, one of the trehalose lipids fractions was identified as a trehalose dimycolate. The presence of (NН) group was detected in the exopolysaccharide. For the first time, a biodegradable polymer was isolated from bacteria cells of the strain R. erythropolis Au-1, іt was identified as the polyhydroxyalkanoate. The physico-chemical properties of the metabolites of the strain R. erythropolis Au-1 were established: the surface tension of trehalose lipids fractions was 30,5-43,2 mN/m; the emulsification activity of the exopolysaccharide solutions (1-10 g/L) with vaseline oil was 42-58%. The differential thermal analysis was used to define starting temperatures of degradation of trehalose dimycolate (130 °C), exopolysaccharide (180 °C) and polyhydroxyalkanoate (164 °C, melting point 42oC). The obtained results expand the possibilities of practical application of trehalose lipids, exopolysaccharide and polyhydroxyalkanoate of the strain R. erythropolis Au-1.

The growing concern over the long-term persistence of plastic waste has driven research into biological methods of breaking down polymers. This study investigated a process that combines physicochemical pretreatment and biodegradation of low-density polyethylene (LDPE) using bacterial strains isolated from commercial compost. Four bacterial strains were genetically identified and classified as Actinomycetes. Exposure of LDPE to these selected strains resulted in a measurable reduction in polymer sample weight, accompanied by alterations in surface hydrophobicity. Furthermore, the chemical modifications at the films’ surfaces were confirmed by the spectra obtained by Fourier transform infrared spectroscopy (FTIR). The microbial colonisation of plastic surfaces plays a key role in the overall biodegradation process. The formation of a biofilm and the subsequent morphological changes on the LDPE surface were revealed by scanning electron microscopy (SEM). The modification of the polyethylene surface by nitric acid treatment was found to be a promising strategy for enhancing the LDPE degradation. The acid-treated films exhibited the greatest weight loss, the greatest increase in carbonyl index values, and the greatest change in hydrophobicity following microbial exposure. Moreover, it was found that biodegradation under these conditions resulted in the lowest levels of phytotoxic byproducts. The transformation of polyethylene surface properties—from hydrophobic to hydrophilic—combined with the presence of oxidized functional groups made it easier for microorganisms to degrade LDPE.

The influence of biosurfactants of trehalose lipid nature (R. erythropolis Au-1) and rhamnolipid nature ( Pseudomonas sp. PS-17) on the efficiency of the absorption of K+ and Ca2+ ions and plants growth was studied. The seeds of soybean, wheat and sunflower after the pre-sowing treatment by the biosurfactants solutions were grown on a liquid nutrient medium. The residual contents of K+ and Ca2+ ions in the medium were different for the variants with the biosurfactants and control (water). Based on these parameters, it was possible to value the stimulating effect of the biosurfactants on the plants’ ability to absorb mineral elements from the nutrient medium. The plants after the pre-treatment by the biosurfactants absorbed on 10-40% (trehalose lipids) and 27-61% (rhamnolipid biosurfactants) K+ and Ca2+ ions more than control variants. The growth parameters of plants were increased on 17-24% (trehalose lipids) or 39-77% (rhamnolipid biosurfactants). The experiments with plants (wheat, soya and sunflower) were also conducted in field conditions. The results showed that the trehalose lipid and rhamnolipid biosurfactants provide an increase in crop yields on 19-23% as well as the yield quality. The obtained data allowed to suggest a possible mechanism for the influence of surfactants on the plant growth.

Plastics have become indispensable in everyday life due to their properties. For this reason, the accumulation of polymer waste in the natural environment is becoming a serious global problem. The aim of the research was to isolate microorganisms capable of biodegrading plastics. The studies focused on the biodegradation of low-density polyethylene as the most common polymer. Seven and five bacterial strains were isolated from the landfill and compost, respectively. The morphological and biochemical characteristics of the isolates were determined. These isolates were able to survive in an environment where the only carbon source was LDPE, but no increase in biomass was obtained. However, analysis of the spectra obtained by the ATR-FTIR method showed the formation of chemical changes on the polymer surface. Bacterial biofilm formation was visualized by scanning electron microscopy. The toxicity of plastic biodegradation products in a liquid environment was tested and their safety for plants was confirmed. However, these biodegradation products have acute lethal toxicity for the Daphnia magna. LDPE films were pre-treated with H 2O 2, HNO 3, or heat. The biodegradation of HNO 3-treated LDPE by isolated bacteria was the most significant. The weight loss was approximately 8%, and 6%, for landfill and compost-isolated bacterial strains, respectively.