Biodegradation of Plastic Beads-derived Polyethylene Microplastics by Penicillium species Isolated from Soil 

Plastic (polyethylene (PE)) beads, which come in a variety of colors and forms, are a versatile, lightweight, and inexpensive craft material commonly used in different applications including jewelry making, decorating, painting, construction, cake designing, food packaging, etc. However, due to their high resistance to degradation, waste from PE beads can persist and accumulate in the environment over long periods, posing a significant ecological threat. Bioremediation is regarded as an effective and environmentally friendly waste removal strategy. Therefore, the present study focuses on the degradation of PE microplastic particles (PE MPP) from commercial PE beads by soil microorganisms. Two fungal species were isolated from field soil with promising potential to biodegrade pristine PE MPP (≤125 µm), and they were identified as Penicillium sp. and Penicillium olsonii based on morphological and ITS region analyses. For biodegradation studies, PE MPP were incubated with the Penicillium strains in mineral salt medium for 30 d at 28oC and 150 rpm. After 30 d incubation, the PE MPP cultured with Penicillium sp. and P. olsonii showed weight losses of 5.25% and 2.94%, respectively. Also, surface cracks and perforations were observed in the biodegraded PE MPP under a scanning electron microscope, and the FTIR analysis further revealed surface structural changes. In addition, two PE-degrading enzymes, laccase and manganese peroxidase were detected in the PE MPP culture media by spectrophotometric assay. These results demonstrate that Penicillium sp. and P. olsonii can be promising candidates for PE bioremediation.

Keywords: Biodegradation, Laccase, Manganese peroxidase, Microplastic, Plastic beads, Soil fungi