Plastic Degradation by Extremophilic Microbial Communities Isolated from Bulgaria and Russia

This work reports the potential impact of extremophiles in resolving one of the biggest contemporary ecological problem - accumulation of huge amounts of plastic pollutants. Lye (C1) and water mud (C2) from Atanasovsko ezero, Bulgarian salterns were enriched for 2 weeks in a mineral salt medium provided with four synthetic plastics, Polycaprolactone (PCL), Polyvinyl alcohol (PVA), Polystyrene (PS), and Polypropylene (PP). Esterase activity was established for C1 on PVA and for C2 - on PCL and PVA. Scanning electron microscopy analysis of the plastics showed most explicit alterations on PCL surface. While the presence of C1 in the culture medium caused damage of the plastic surface, C2 interacted with it directly by forming a biofilm in surface breaks. Metagenomic analysis of C2, control and C2 with PCL revealed lower phylogenetic diversity in the presence of PCL and sharp rise of Gammaproteobacteria 16S rRNA sequences. The flourishing of the family Halomonadaceae was accompanied by a strong domination of the genus Halomonas, suggesting its active participation in PCL degradation. Thermophilic microorganisms in samples from Kamchatka hot springs were enriched in a medium with high- and low-density polyethylene in anaerobic conditions, at 78 oC. Degradation of polyethylene after incubation was monitored by SEM. Results of 16S rRNA genes profiling compared with control variants revealed a domination of bacteria of phylum Dictyoglomi and family Thermoanaerobacteraceae in anaerobic thermophilic Kamchatka enrichments in the presence of polyethylene. These results indicate the possibility of thermophilic anaerobes to degrade the two types of polyethylene.