Polyhydroxyalkanoates from industrial cheese whey: Production and characterization of polymers with differing hydroxyvalerate content

Abstract

The composition of polyhydroxyalkanoate (PHA) monomers affects the properties and final applications of PHA polymers. This study focused on the feasibility of producing tailored PHA differing in hydroxyvalerate (HV) content, through manipulation of the acidogenic fermented stream composition, and on the characterization of PHA properties to determine the best composition for melt processing. Cheese whey was used as a feedstock, and changes in the organic loading rate during acidogenic fermentation led to the production of a fermented stream with an HV precursor content of 9–33 wt%. In the PHA production assays, a PHA content of 50 ± 11 wt%. (VSS basis) and yield of 0.76 ± 0.14 gCODPHA.gCODFP-1 were obtained. Fermented stream supplementation with HV precursors during the PHA accumulation assays indicated the feasibility of producing tailored PHA with differing HV content without a need for the selection of new cultures. The thermal properties of PHA were found to be controlled by the HV content, and PHA with approximately 30 wt% HV had the lowest melting temperature. These results demonstrated the robustness of the process at pilot scale, thus supporting full-scale applications in tailored PHA production.

Keywords

• Pilot Scale
• Cheese whey valorization
• Biodegradable biopolymers
• Hydroxyvalerate content
• Thermal properties