Mountains of plastic waste consisting of carrier bags and medical packaging are buried in landfill sites dumped in rivers around the world annually. Unfortunately plastics generated by the petrochemical industry are not biodegradable and therefore accumulate in the environment at a rate of over 25 million tones year-1. Therefore there is a huge demand for biodegradable plastics. Polystyrene (PS), polyethylene (PE) and polypropylene (PP) are problematic materials, used for appliance housings, disposable cutlery and general packaging. This study investigates the utilisation of waste PS, PE and PP as a potential additional carbon sources using bacteria to synthesise polyhydroxyalkanoates (PHAs); a value-added material, able to replace some conventional fossil-fuel plastics while being non-toxic, fully biodegradable and biocompatible. Prodegraded waste PS and PP, and thermally treated PEwere used as supplementary carbon sources totryptone soya broth (TSB and BSM) for 48 h fermentations [1, 2, 3]. The bacterial strain Cupriavidus necator H16 was selected as it is non-pathogenic, genetically stable, robust and one of the best natural producers of PHA. The accumulation of PHAs varied from 17 % (wt / wt) of dry biomass in TSB controls to 39–66 % for PS, PE and PP thermally treated samples. The polymers obtained were analysed with nuclear magnetic resonance (NMR) and electrospray ionisation tandem mass spectrometry (ESI-MS/MS) to characterise their chemical structure. In conclusion, certain thermal treatment protocols of the waste plastics were shown to be viable for PHA production; with3-hydroxybutyrate and up to 12 mol% of 3-hydroxyvalerate and 3-hydroxyhexanoate co-monomeric units formed.

  • This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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