Development and Characterization of Electrospun Biopapers of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Derived from Cheese Whey with Varying 3-Hydroxyvalerate Contents

Abstract

In the present study, three different newly developed copolymers of poly(3-hydroxybutyrate- co -3-hydroxyvalerate) (PHBV) with 20, 40, and 60 mol % contents in 3-hydroxyvalerate (3HV) were produced by the biotechnological process of mixed microbial cultures (MMCs) using cheese whey (CW), a by-product from the dairy industry, as feedstock. The CW-derived PHBV copolyesters were first purified and then processed by solution electrospinning, yielding fibers of approximately 2 μm in cross-section in all cases. The resultant electrospun PHBV mats were, thereafter, post-processed by annealing at different temperatures, below their maximum of melting, selected according to their 3HV content in order to obtain continuous films based on coalesced fibers, so-called biopapers. The resultant PHBV films were characterized in terms of their morphology, crystallinity, and mechanical and barrier properties to assess their potential application in food packaging. The CW-derived PHBV biopapers showed high contact transparency but a slightly yellow color. The fibers of the 20 mol % 3HV copolymer were seen to contain mostly poly(3-hydroxybutyrate) (PHB) crystals, the fibers of the 40 mol % 3HV copolymer a mixture of PHB and poly(3-hydroxyvalerate) (PHV) crystals and lowest crystallinity, and the fibers of the 60 mol % 3HV sample were mostly made of PHV crystals. To understand the interfiber coalesce process undergone by the materials during annealing, the crystalline morphology was also assessed by variable-temperature both combined small-angle and wide-angle X-ray scattering synchrotron and Fourier transform infrared experiments. From these experiments and, different from previously reported biopapers with lower 3HV contents, all samples were inferred to have a surface energy reduction mechanism for interfiber coalescence during annealing, which is thought to be activated by a temperature-induced decrease in molecular order. Due to their reduced crystallinity and molecular order, the CW-derived PHBV biopapers, especially the 40 mol % 3HV sample, were found to be more ductile and tougher. In terms of barrier properties, the three copolymers performed similarly to water and limonene, but to oxygen, the 40 mol % sample showed the highest relative permeability. Overall, the materials developed, which are compatible with the Circular Bioeconomy organic recycling strategy, can have an excellent potential as barrier interlayers or coatings of application interest in food packaging.

Effect of 3-Hydroxyvalerate Content on Thermal, Mechanical, and Rheological Properties of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Biopolymers Produced from Fermented Dairy Manure

“…Shorter chains need less time for crystallization compared to longer chains which results in reduction of T c [ 49 ]. A T c value ranging from 41 to 82 °C for CHCl 3 extracted PHBV with 3HV contents of (20–60%) have been reported [ 50 ]. Another study had shown that PHBV (16.6% HV) extracted with NaClO and CHCl 3 had a T c value of 109 °C [ 51 ].…”

Exploitation of wasted bread as substrate for polyhydroxyalkanoates production through the use of Haloferax mediterranei and seawater

“…However, the conventional extraction/purification procedure adopted for obtaining pPHBV led to the recovery of a copolymer with a slightly lower ratio of HV. The HV content impacts the thermal and mechanical properties of the stored polymer and, in turn, its final application, as widely reported in the literature ( Melendez-Rodriguez et al, 2021 ).…”

Model-aided targeted volatile fatty acid production from food waste using a defined co-culture microbial community

“…The higher selectivity for odd-carbon VFA strategy can be of use in applications as, for example, the production of bioplastics as polyhydroxyalkanoates (PHA). PHA are bio-sourced biodegradable polyesters that can be produced biologically using VFA as substrate and that require a balanced mixture of odd-and even-carbon VFA to have properties that allow them to effectively substitute current oil-based polymers (Duque et al, 2014;Melendez-Rodriguez et al, 2021). If the VFA mixture obtained in the base case would be used for the synthesis, the obtained PHA would instead have much poorer mechanical properties, limiting the use for common applications such as packaging films (Cunha et al, 2016).…”