Milica Ćirić1*, Clémence Budin2, Tjalf de Boer2, Brana Pantelić1 and Jasmina Nikodinović-Runić1
1 Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, Belgrade, Serbia
2 Microlife Solutions, Amsterdam, The Netherlands
milica.ciric [at] imgge.bg.ac.rs
Abstract
Global research efforts to develop biocatalytic processes based on microbial enzymes to alleviate plastic pollution are underway. Despite a proposed overlap between enzymatic capacity to degrade plastics and lignocellulosic biomass, bioprospecting efforts to identify microorganisms capable of degrading both types of substrates remain limited.
Plastic and lignocellulose degrading potential of 15 bacterial isolates from polluted Serbian soils, belonging to genera detected with abundance >1% in virgin plastics (LLDPE)- or post-consumer representative mixed plastics (MS)-enriched 16S metagenomes, was explored. Plastic polymers Impranil® DLN-SD (SD) and DL2077 (DL), bis(2-hydroxyethyl) terephthalate (BHET), polycaprolactone diol (PCL) and polylactic acid (PLA) and lignocellulosic polymers carboxymethyl cellulose (CMC), arabinoxylan (AXYL) and lignin (LIG) were provided as sole carbon source for the isolates.
16S rDNA dendrogram of 9 LLDPE-enriched isolates from genera Lysinibacillus, Rhodococcus, Hydrogenophaga, Pseudomonas, Nocardoides and Psychrobacillus and 6 MS-enriched isolates from genera Pseudomonas, Advenella and Paenibacillus showed no clear grouping, suggesting that relatively distinct isolates were selected for the screening. No zones of clearing, indicating complete substrate degradation is taking place, were observed. Single Advenella isolate demonstrated growth on all plastic substrates, while 11 isolates demonstrated growth on PCL, 10 on BHET, 6 on SD, 4 on DL and 4 on PLA. Fourteen isolates grew on all tested lignocellulosic substrates.
Genome mining of 3 sequenced isolates using PAZy database identified putative PU-, PET-, PCL- and PLA-active enzymes in both Hydrogenophaga, growing on all plastic substrates except PLA and Pseudomonas, growing on BHET and PCL, while Lysinibacillus, with predicted PCL and PLA activities, demonstrated no growth on any of the tested plastic substrates. Lignocelullolytic enzymes (GHs, CEs, PLs and AAs) were also predicted in these isolates, demonstrating growth on all tested lignocellulosic substrates, using CAZy database.
Investigated isolates should be further explored using a wider range of plastic substrates and screening conditions.
Keywords: soil, 16S metagenomics, genome mining, PAZy, CAZy
Acknowledgement: This work was supported by the EU H2020 Research and Innovation Programe (grant agreement No. 870292, BioICEP) and by the Ministry of Science, Innovation and Technological Development of the Republic of Serbia (agreement No. 451-03-66/2024-03/200042). 16S rDNA sequences are deposited in the NCBI GeneBank database (accession numbers: PP594182-PP594194). 16S metagenomic and genome sequences are available upon request.