Recently, Associate Professor Yanping Mao's team from the College of Chemistry and Environmental Engineering at Shenzhen University published the latest research progresses 《Genomic insights and metabolic pathways of an enriched bacterial community capable of degrading polyethylene》 on journal《Environment International》(2023 IF: 10.3; 5 year IF: 11.2).    

Graphical Abstract

Facing the increasingly severe global plastic pollution challenge, especially the issue of microplastic (MPs) pollution, microbial degradation is one of the sustainable solutions. A key factor in promoting the development of this technology is to explore highly efficient plastic-degrading microorganisms in different habitats. Among them, activated sludge has attracted much attention because it contains a microbial community occupying diverse ecological niches. In this study, polyethylene (PE) plastic was used as a carbon source to enrich and culture the activated sludge microbiota to screen for microbial communities capable of degrading PE. After 28 days of enrichment culture, the weight loss of the PE film reached 3%, and its hydrophobicity decreased. Meanwhile, Fourier-transform infrared spectroscopy (FTIR) results showed that multiple new oxygen-containing functional groups were formed on the PE surface. Microbial analysis extracted 26 metagenome-assembled genomes (MAGs) from the enriched microbial communities. Among them, MAG10, MAG21 and MAG26 increased significantly in abundance after PE addition and were rich in genes related to carbohydrate transport and metabolism. Functional analysis further identified 14 plastic-degrading-related functional genes, including oxidases, laccases and lipases, suggesting that this microbiota has the potential to degrade PE.

Based on the potential PE-degrading genes carried by MAG10, this study proposes a new approach for the microbial consortium to degrade PE plastic synergistically. Alkanes first enter the periplasm through the TonB system and then enter the cytoplasm via ABC transporters in the bacterial inner membrane. AlkB is also an inner membrane protein that can act as a carrier protein to transport alkanes and catalyze the conversion of alkanes into alcohols. However, MAG10 does not encode AlkB, so the hydroxylation of alkanes may be carried out by cytochrome P450. Unlike AlkB, which can only hydroxylate terminal and subterminal alkanes, cytochrome P450 can hydroxylate alkanes at different carbon positions (terminal, subterminal, and chain-middle). Therefore, after alkanes are hydroxylated by cytochrome P450 in MAG10, they are subsequently converted into primary and secondary alcohols. Primary and secondary alcohols are oxidized to acetic acid and long-chain fatty acids through a series of cascade enzyme-catalyzed reactions inside the cell. The generated acetic acid and long-chain fatty acids are respectively synthesized into acetyl-CoA and acyl-CoA, which then enter the TCA cycle and β-oxidation cycle respectively. Finally, the metabolic products and biodegradation products of PE are assimilated or mineralized into biomass, CO₂ and H₂O through intracellular enzymatic pathways.

Metabolic pathway of PE degradation inferred from the genome

Full-text link：https://doi.org/10.1016/j.envint.2025.109334