Tailoring Pseudomonas putida feedstocks for enhanced medium-chain-length polyhydroxyalkanoate production and biomedical nanoemulsion applications

The environmental challenges posed by conventional plastics can be addressed by using bioderived and biodegradable medium-chain-length polyhydroxyalkanoates (mcl-PHAs) produced by Pseudomonas putida KT2440, a microorganism renowned for its versatile biopolymer synthesis capabilities. This study evaluated mcl-PHA production and its properties for packaging and biomedical applications. We investigated the combined use of fatty acids and glucose, which can be derived from food waste, as a sustainable and cost-effective feedstock strategy. Substituting decanoic acid (F10) and dodecanoic acid (F12) with glucose maintains consistent monomer composition, and a 50% glucose substitution in the F12 feedstock boosts the PHA content to 66% in Pseudomonas putida, reducing cell dry weight to 6 g/L while keeping a similar PHA yield of 4 g/L. This approach offers a practical way to reduce costs and maintain polymer quality, boosting its appeal for industrial-scale production. The resulting mcl-PHA was able to form nanostructures via the formation of a nanoemulsion, with sizes between 120 and 350 nm and low dispersity (<0.2). Nanostructure size was influenced by the fatty acid feedstock's chain length, with higher C12 content from F12 producing smaller structures (154 nm), while lower C12 content from F10 resulted in larger structures (207 nm). These nanostructures remained stable for a week under physiological pH but exhibited changes at pH 2, indicating a pH-sensitive platform. This finding opens avenues for developing sustainable, functional biomaterials with potential applications in drug delivery. Overall, this study presents a novel, sustainable approach to high-quality mcl-PHA production. The use of feedstocks that can be derived from food waste and the development of pH-sensitive nanostructures highlight the potential for creating environmentally responsible and functional biomaterials.