Scalable Biosynthesis & Recovery of Poly-3-Hydroxybutyrate Produced from Cotton-Derived Glucose by <em>Ralstonia eutropha</em>

To combat the growing issue of petroleum plastic waste, alternative bio-based polymers are being developed. Many of these biopolymers are made from bio-derived materials, or are biodegradable, but the most promising polymers fall in both categories. Polyhy-droxyalkanoates (PHAs) are one such class of polymers, and poly-3-hydroxybutyrate (P3HB), the most popular PHA, has shown great potential. A large drawback to large scale use of P3HB is the cost of its production. Production from local waste carbon sources, in largescale bioprocessing equipment, and using less chemically intensive extraction, drastically reduces P3HB’s cost. In America, the cotton industry offers millions of tons of cellulosic waste each year that can be transformed into a glucose solution. This study utilized two types of cotton-derived glucose, alongside commercial glucose, as a feedstock for the biosynthesis of P3HB by Ralstonia eutropha. The fermentation took place in a 2-L bioreactor, showing potential for scale-up, and a single-solvent extraction method was used, reducing chemical consumption. The resulting P3HB samples were compared to each other and to the literature based on polymer yield and thermal characteristics. First, while all samples averaged a smaller yield than seen in literature, the cotton-derived glucose was shown to yield more P3HB than commercial glucose. Further, cotton-derived P3HB had very similar thermal properties to the commercial glucose-derived P3HB. Lastly, all samples were shown to have a similar percent crystallinity, though slightly lower than that seen in literature. P3HB made from cotton-derived glucose was shown to have potential as a scalable, sustainable alternative process.