Periphytic biofilm: An innovative approach for biodegradation of microplastics.

Microplastics (MPs) have been gaining the attention of environmental researchers since the 1960s anecdotal reports of plastic entanglement and ingestion by marine creatures. Due to their increasing accretion in aquatic environments, as well as resistance towards degradation, marine litter research has focused on microplastics more recently. In the present study, a relatively new method of biodegradation was implemented for the biodegradation of three structurally different MPs i.e. polypropylene (PP), polyethylene (PE) and polyethylene terephthalate (PET). Periphytic biofilm was used for this purpose in various backgrounds of carbon sources (glucose, peptone, and glucose and peptone). Biodegradation of MPs was estimated in terms of weight loss. It was observed that the addition of glucose enhanced the biodegradation of MPs by periphyton biofilm for all MPs (from 9.52%–18.02%, 5.95%–14.02% and 13.24–19.72% for PP, PE and PET respectively) after 60 days compared to natural biofilm alone. To the contrary, peptone, and glucose and peptone together, were inhibitory. Biodegradation was further confirmed by morphological changes observed using SEM, FTIR spectra and GPC lent further support to the results whereby new peaks appeared along with reduction in old peaks and decrease in peak intensities. MiSeq sequencing shows that Deinococcus-thermus > Proteobacteria > Cyanobacteria are the dominant phyla in natural biofilms, and their relative abundances increase after the addition of glucose. However, the abundances shifted to Deinococcus-thermus > Cyanobacteria > Firmicutes > Bacteroidetes , when the biofilms were treated with either peptone alone, or with glucose and peptone together. Therefore, the change in biodegradation capability might also be due to the change in the microbial community structures after addition of the C-sources. These experiments provide an innovative approach towards effective biodegradation of MPs using a relatively new environment-friendly method. Unlabelled Image • Immobilized periphytic biofilms were implemented for the biodegradation of MPs. • Glucose proved to be the most effective C-source for effectual MPs' biodegradation. • SEM and FTIR confirm biodegradation showing morphological and structural changes. • MiSeq sequencing shows that C-sources affects microbial community structure. • Periphytic biofilms are eco-friendly entities effectual for MP biodegradation. [ABSTRACT FROM AUTHOR]