116k Production of Poly (3-Hydroxybutyric Acid) from Waste Sweet Potato Starch

James D. Winkler1, Ratna Sharma2, and Mari S. Chinn2. (1) Chemical Engineering, Rice University, 6330 Main Street, Houston, TX 77005, (2) North Carolina State University, Campus Box. 7625, Biological and Agricultural Engineering, Raleigh, NC 27695, United States

The organism Ralstonia eutropha has been reported to produce Poly (3-Hydroxy-butyric Acid) (PHB), a valuable biodegradable polymer. PHB synthesis in R. eutropha occurs during periods of transient nutrient deprivation in order to sequester carbon in anticipation of a restoration of better growth conditions. Artificial nutrient (primarily nitrogen or phosphorus) limitation is therefore used to induce large scale PHB production in the organism. The mechanical properties of PHB synthesized depend heavily on the carbon source used; the desired properties of the polymer can be controlled by carefully selecting the feedstock used as the carbon substrate for R. eutropha. This project investigated the novel use of a hydrolyzed industrial sweet potato (FTA-94) starch in an effort to determine whether PHB could be produced from the substrate and how the choice of feedstock would influence properties of the resulting polymer. Cultures incubated in FTA-94 limited media exhibited significant PHB inclusions under transient electron microscope (TEM) imaging. Gas chromatographic analysis of cell samples confirmed the presence of PHB.The results demonstrate that FTA-94 can serve as the sole carbon substrate for PHB synthesis without causing undesired inhibitory effects on bacterial growth. Further analyses are expected to reveal average molecular weight and compositional information of chemically extracted PHB.