Marine biodegradability of bio-based and petroleum-based polymers as substitutes of conventional microbeads

, Ghiglione Jean-François, Cheng Jingguang, Boris Eyheraguibel, Ter Halle Alexandra, Bruzaud Stéphane, Meistertzheim Anne-Leïla.

The European parliament voted to ban single-use plastic items in 2021 and transition to bio-economy includes the substitution of these banned products by biodegradable polymers. Conventional plastic microbeads classically used as abrasive agents and excipients in cosmetics contribute worldwide to more than 4% of primary microplastics discharged each year into the marine environment, i/e. between 10,900 and 38,300 tonnes / year. Here, we tested the potential of the marine “plastisphere” to biodegrade microbeads composed of petroleum-based polymers (PCL, PMMA), bio-based (PHBV, PLA) and natural products (rice, apricot) as compared to conventional PE-based polymer. After colonization of the microbeads by a microbial biofilm in circulating aquariums open to the sea for 2 months (Banyuls Bay, Mediterranean), their biodegradation was studied for an additional 2 months after transfer in a minimum medium with microbeads as the only carbon source. We used a multidisciplinary approach including changes in the physical properties (particle size, molecular weight) and chemical properties (production of oligomers) of the microbeads. Changes in microbial abundance, diversity and activity were explored by confocal microscopy, flow cytometry, Illumina sequencing, heterotrophic prokaryotic activity, energy production (ATP) and respiration (O2). This multidisciplinary approach showed efficient biodegradation of the biobased PHBV and the petroleum-based PCL, whereas biobased PLA did not show sign of biodegradation in our marine conditions. We were able to identify specific OTUs directly linked with biodegradation activities proved by the coupled chemical and biological tools. Metagenomic analysis are currently under analysis that will help to decipher the polymer degradation mechanisms under marine conditions. Finally, this work led to the development of a ministerial decree and our protocol was the subject of a SOLEAU envelope.

View online