Valorization of Municipal Biowaste into Electrospun Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Biopapers for Food Packaging Applications

The present study reports on the production and characterization of a new biopackaging material made of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) derived from municipal biowaste (MBW) and produced by the mixed bacterial culture technology. After purification and extraction, the MBW-derived PHBV was processed by electrospinning to yield defect-free ultrathin fibers, which were thermally post-treated. Annealing at 130 °C, well below the biopolymer’s melting temperature (Tm), successfully yielded a continuous film resulting from coalescence of the electrospun fibrillar morphology, the so-called biopaper, exhibiting enhanced optical and color properties compared to traditional melt compounding routes. The crystallinity and crystalline morphology were comprehensively studied as a function of temperature by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy and combined time-resolved synchrotron small- and wide-angle X-ray scattering (SAXS and WAXS) experiments, which clearly indicated that the molecular order within the copolyester was improved up to a maximum at 130 °C, and then it decreased at the biopolymer’s Tm. It was hypothesized that by annealing at the temperature at which the thermally induced molecular order is maximized, the fibers generated sufficient mobility to align alongside, hence reducing surface energy and porosity. The data suggest that this material shows a good balance between enhanced mechanical and improved barrier properties to vapors and gases in comparison to traditional paper and other currently used petroleum-derived polymers, thus presenting significant potential to be part of innovative food biopackaging designs for the protection and preservation of foods in a circular bioeconomy scenario.The Spanish Ministry of Science and Innovation (MICI) project RTI2018-097249-B-C21 and EU projects H2020 YPACK (reference number 773872) and H2020 USABLE (reference number 836884) are acknowledged for funding support. B.M.-R. and S.T.-G. would also like to thank MICI for the FPI fellowship (BES-2016-077972) and the Juan de la Cierva–Incorporación contract (IJCI-2016-29675), respectively. The ALBA Synchrotron, Spain, is also acknowledged for the funding received through the project proposal 2018022619. The authors also thank the “Unidad Asociada CSIC-UJI in Polymers Technology”.Peer reviewe