The increasing concern over the environmental impacts of conventional petroleum-based, non-biodegradable plastics has driven the development of innovative bio-based polymers (bioplastics) as more sustainable alternatives. However, knowledge of the microbial biofilms associated with these materials remains limited. Improving our understanding of biofilm colonization is essential for evaluating the environmental degradation of biopolymers and assessing their suitability as environmentally compatible materials in the event of accidental release.
In this study, biofilm development on two biodegradable polymers, poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBv) and polylactic acid (PLA), was investigated in a marine environment and compared with that on a conventional plastic, polypropylene (PP). The experiment was conducted in mesocosms deployed in the Baltic Sea over a three-week period (June 2023). Plastic sheets were thermoformed, cut into 20 × 20 mm fragments, and mounted on frame holders containing nine replicates of each polymer.
Biofilm formation, prokaryotic abundance, and microbial community composition were characterized using 16S rRNA gene metabarcoding. Sequence reads assigned to eukaryotes were also examined. Biofilms developed on all tested polymers, with biomass increasing over time and photosynthetic organisms becoming evident after three weeks of exposure. Distinct prokaryotic communities were associated with each polymer and with the control samples. Prokaryotic abundance generally declined throughout the exposure period, with the exception of PLA. Community composition also varied among polymer types: the biofilm associated with conventional PP more closely resembled that of the surrounding seawater, whereas PLA and PHBv supported microbial communities that were more similar to each other. Overall, these results indicate that microbial colonization is influenced by polymer type, with biodegradable plastics promoting the establishment of distinct bacterial biofilm communities during the early stages of marine exposure.