| Summary: | Meeting the challenge of circularity for plastics requires amenability to repurposing post-use, as equivalent or upcycled products. In a compelling advancement, complete circularity for a biodegradable polyvinyl alcohol/thermoplastic starch (PVA/TPS) food packaging film was demonstrated by bioconversion to high-market-value biopigments and polyhydroxybutyrate (PHB) polyesters. The PVA/TPS film mechanical properties (tensile strength (<i>σ</i><sub>u</sub>), 22.2 ± 4.3 MPa; strain at break (<i>ε</i><sub>u</sub>), 325 ± 73%; and Young’s modulus (<i>E</i>), 53–250 MPa) compared closely with low-density polyethylene (LDPE) grades used for food packaging. Strong solubility of the PVA/TPS film in water was a pertinent feature, facilitating suitability as a carbon source for bioprocessing and microbial degradation. Biodegradability of the film with greater than 50% weight loss occurred within 30 days of incubation at 37 °C in a model compost. Up to 22% of the PVA/TPS film substrate conversion to biomass was achieved using three bacterial strains, <i>Ralstonia eutropha</i> H16 (<i>Cupriavidus necator</i> ATCC 17699), <i>Streptomyces</i> sp. JS520, and <i>Bacillus subtilis</i> ATCC6633. For the first time, production of the valuable biopigment (undecylprodigiosin) by <i>Streptomyces</i> sp. JS520 of 5.3 mg/mL and the production of PHB biopolymer at 7.8% of cell dry weight by <i>Ralstonia eutropha</i> H16 from this substrate were reported. This low-energy, low-carbon post-use PVA/TPS film upcycling model approach to plastic circularity demonstrates marked progress in the quest for sustainable and circular plastic solutions.
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