Alessandro Rimmaudo A.Rimmaudo@napier.ac.uk
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Microplastics in organic waste-derived materials: quantification, and assessment of associated bacterial community and its antimicrobial resistance
Rimmaudo, Alessandro
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Abstract
This study aimed to quantify and characterise microplastics in organic-rich waste materials: biosolids, compost, and anaerobic digestates, and investigate their associated bacterial community and potential role in the spreading of AMR. A cost-effective method based on organic matter oxidation, differential flotation, and vacuum filtration was developed to isolate microplastics from these matrices and were quantified and characterised via microscopy. The results showed that all analysed waste samples contained elevated concentrations of microplastics, with concentrations ranging from 34 to 160 particles per gram of dry weight. Fibres were found to be the most abundant morphology, representing 48-71% of the microplastics, followed by fragments, beads, and other types. The study also detected > 20,000 particles g-1 d.w. of cotton fibres in biosolids. To investigate the potential role of microplastics as microbial niches and vectors of antibiotic-resistance, biofilms associated with polyester fibres, polyethylene beads, and cotton fibres after seven days of incubation in a biosolid liquid culture were examined in the presence and absence of the antibiotics tetracycline or sulfamethoxazole. The bacterial community growing on particles, investigated using metataxonomic, showed significant differences between fibre and bead types, with antibiotics having a stronger effect on the bacterial community composition of beads. The ARGs tetA, sul1 and MGE intl1 quantified using qPCR, were found to be more abundant on fibres than beads, but antibiotic addition had limited effects on ARG abundance. The relative abundance of ARGs expressed as a proportion of that of the 16S rRNA gene was similar across all biofilms and was not significantly affected by antibiotic addition. The study showed that biosolids are heavily contaminated with microplastics and carry bacterial community and AMR bacteria, representing a major source of microplastic pollution in agricultural land and that microplastics, especially fibres, as well as cotton fibres, may act as potential vectors for the spread of antibiotic-resistance in the environment and food chain.
Citation
Rimmaudo, A. Microplastics in organic waste-derived materials: quantification, and assessment of associated bacterial community and its antimicrobial resistance. (Thesis). Edinburgh Napier University
Thesis Type | Thesis |
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Deposit Date | Sep 4, 2024 |
Publicly Available Date | Sep 4, 2024 |
DOI | https://doi.org/10.17869/enu.2024.3789779 |
Award Date | Jul 3, 2024 |
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Microplastics in organic waste-derived materials: quantification, and assessment of associated bacterial community and its antimicrobial resistance
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