Polyhydroxyalkanoate production from solid waste animal fat and biological downstream processing: A pilot-scale study

Innovative approaches are required to transition from a linear to a circular (bio)economy. Natural plastic alternatives, such as polyhydroxyalkanoates (PHAs), have great potential to promote this transition. In this study, we demonstrate the feasibility of converting solid waste animal fat (WAF) into the PHA copolymer poly(hydroxybutyrate-co-hydroxyhexanoate) (P(HB-co-HHx)) via bacterial fed-batch fermentation at 750-L pilot-scale using the engineered strain Cupriavidus necator Re2058/pCB113. A total of 48 kg of PHA-rich dried cells were produced and subjected to pilot-scale biological downstream processing via mealworms (Tenebrio molitor), resulting in 19 kg of high-purity (>99 %) PHA powder. Material characterization confirmed that the molecular weight remained stable throughout the entire downstream process, which included drum drying, cell wall digestion by mealworms, and final polymer purification using water, sodium hydroxide and sodium hypochlorite.