Characterization of Polystyrene-Degrading Bacteria Isolated From Plastic Processing Plants

This study investigated the occurrence of the most common types of bacteria and fungi on the surfaces of production lines, raw materials, and finished products in plastics processing plants. The total aerobic colony count was confirmed in 42.0% of the samples, followed by moulds (30.0%) and representatives of the genera Bacillus (28.3%) and Staphylococcus (19.9%). Growth on a solid medium with polystyrene was confirmed in 63 (63.4%) of the 96 selected strains, but only 3 (3.0%) of them were able to form a clear zone around the colonies. In addition, the ability of 10 selected bacterial strains to form biofilms and to degrade PS surfaces was determined. The highest weight loss of polystyrene was observed in the presence of Bacillus strains. Depending on the strain, the degradation rate was between 0.12 and 0.78% after 30 days and between 0.21 and 2.15% after 60 days. The number of living cells in biofilms on surfaces was lowest for the Gram-negative strains Burkholderia and Moraxella and highest for most Bacillus and some Micrococcus strains. Fourier transform infrared spectroscopy revealed differences in the ratios of vibrational bands after exposure to bacterial strains, although no oxygen-containing functional groups were observed on the surface of polystyrene samples. The average contact angle values of polystyrene surfaces exposed to the tested bacterial strains decreased from 80.55 ± 0.39° to 73.64 ± 0.45° after 60 days of incubation. Some isolated bacterial strains from plastic production plants show the potential for more intensive degradation of such materials, which could impact the quality and shelf life of plastic products.