Bioconversion Process of Polyethylene from Waste Tetra Pak Packaging to Polyhydroxyalkanoates.

Presented herein are the results of a novel recycling method for waste Tetra Pak packaging materials. The polyethylene (PE-T) component of this packaging material, obtained via a separation process using a "solvents method", was used as a carbon source for the biosynthesis of polyhydroxyalkanoates (PHAs) by the bacterial strain H16. Bacteria were grown for 48-72 h, at 30 °C, in TSB (nitrogen-rich) or BSM (nitrogen-limited) media supplemented with PE-T. Growth was monitored by viable counting. It was demonstrated that utilised PE-T in both growth media, but was only able to accumulate 40% PHA in TSB supplemented with PE-T. Only 1.5% PHA was accumulated in the TSB control, and no PHA was detected in the BSM control. Extracted biopolymers were characterised by nuclear magnetic resonance (NMR), Fourier-transform infrared (FTIR) spectroscopy, electrospray tandem mass spectrometry (ESI-MS/MS), gel permeation chromatography (GPC), and accelerator mass spectrometry (AMS). The characterisation of PHA by ESI-MS/MS revealed that PHA produced by in TSB supplemented with PE-T contained 3-hydroxybutyrate, 3-hydroxyvalerate, and 3-hydroxyhexanoate co-monomeric units. AMS analysis also confirmed the presence of 96.73% modern carbon and 3.27% old carbon in PHA derived from Tetra Pak. Thus, this study demonstrates the feasibility of our proposed recycling method for waste Tetra Pak packaging materials, alongside its potential for producing value-added PHA, and the ability of 14C analysis in validating this bioconversion process.