Chemical free extraction of polyhydroxyalkanoates produced from pilot-scale Haloferax mediterranei fermentation of glycerol waste

Polyhydroxyalkanoates (PHAs) are biodegradable polymers with great mechanical and thermal properties, offering a sustainable alternative to conventional plastics. Despite their advantages, the widespread adoption of PHAs is hindered by the high cost of feedstock in PHA production and downstream separation and purification. This study demonstrates pilot-scale production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) by Haloferax mediterranei using glycerol waste as a low-cost substrate, followed by PHA extraction and purification using high-pressure homogenization (HPH). The results show that under nonsterile conditions, using glycerol waste yield 5.7 g/L cell mass with 38 % PHBV content in cells. HPH-based downstream processing achieved a PHBV recovery efficiency of 85 % and a purity of 90 %. HPH extraction did not alter the thermal properties of native PHBV, except that increasing HPH pressure led to a reduction in molecular weight of 24.6 %. This study highlights the potential of waste glycerol as a viable feedstock and underlines the understanding of how downstream processing conditions influence PHA properties. Optimizing these parameters is crucial to improving the extraction process and enhancing the application value of PHAs.