Milica Ciric1*, Brana Pantelic1, Vladimir Šaraba1, and Jasmina Nikodinovic-Runic1
1Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, Vojvode Stepe 444a
11000 Belgrade, Serbia
milica.ciric [at] imgge.bg.ac.rs
Abstract
Plastic waste is a global environmental burden. Polyurethanes (PU), toxic and ubiquitous synthetic polymers, do not biodegrade quickly, leading to their rapid accumulation in the soil and water environments. Highly efficient PU-degrading microorganisms are rare in nature and are of fundamental importance for achieving circular plastic economy. Bacterial isolates from groundwater, originating from magmatogenic massif and Tertiary basin within metamorphic area, as well as soil isolates collected from various pristine (PS) and contaminated sites (CS), were screened using PU model compound Impranil® DLN-SD (IMP) as sole C source to identify PU-degrading isolates. Phylogenetic analysis of 16S rRNA gene sequences from IMP-degrading isolates was performed using the neighbor-joining method to observe their clustering. Thirty one of 96 isolates (32.3 %) from groundwater and 18 of 220 isolates (8.2%) from soil produced prominent IMP-clearing zones. Thirteen IMP-degrading isolates from each type of environment, belonging to 8 genera (Pseudomonas, Proteus, Enterobacter, Flavobacterium, Serratia, Pantoea, Acinetobacter and Stenotrophomonas) for groundwater and to 6 genera (Streptomyces, Pseudomonas, Rhodococcus, Achromobacter, Bacillus and Paenibacillus) for soil environment, were included in phylogenetic analysis. No clear grouping of groundwater and soil isolates was observed, indicating that isolates are too distinct. Stronger clustering was observed for groundwater compared to soil isolates. For groundwater, strongest clustering was observed for 2 isolates belonging to Proteus genus, 2 belonging to Flavobacterium and 2 to Pseudomonas. For soil samples, strongest clustering was observed for 3 isolates belonging to genus Streptomyces. There was no clear grouping within isolates from CS and PS. In the future, wider range of environmental niches should be included in screening efforts for development of biocatalytic processes for management of plastic waste. Subterranean ecosystems, which are not readily accessible for sampling and represent largely unexplored reservoir of biotechnologically relevant enzymatic activities, should also be more represented in such screenings.
Keywords: groundwater, soil, polyurethane-degrading bacteria, 16S phylogeny
Acknowledgement: This work was supported by the EU H2020 Research and Innovation Programme (grant agreement No. 870292, BioICEP) and by the Ministry of Science, Innovation and Technological Development of the Republic of Serbia (agreement No. 451-03-47/2023-01/ 200042). 16S rDNA sequences are deposited in the NCBI GeneBank database (accession numbers: OQ991477-OQ991494) for groundwater isolates and at https://doi.org/10.3390/catal13020278 for soil isolates.
