Polymer Films of Poly-3-hydroxybutyrate Synthesized byCupriavidus necatorfrom Different Carbon Sources

Films were prepared from 2% solutions of biodegradable poly-3-hydroxybutyrate [P(3HB)] and investigated. The polymer was synthesized by the Cupriavidus necator B-10646 bacterium cultivated using various carbon sources (glucose and glycerol of different degrees of purity, containing 0.3 to 17.93% impurities). Glycerol as the substrate influenced molecular-weight properties and crystallinity of the polymer without affecting its temperature characteristics. The P(3HB) specimens synthesized from glycerol had reduced M_w (300–400 kDa) and degree of crystallinity (50–55%) compared to the specimens synthesized from glucose (860 kDa and 76%, respectively). The low-crystallinity P(3HB) specimens, regardless of the degree of purity of glycerol, produced a beneficial effect on the properties of polymer films, which had a better developed folded surface and increased hydrophilicity. The values of the highest roughness (R_a) of the films synthesized from glycerol were 1.8 to 4.0 times lower and the water angles 1.4–1.6 times smaller compared to the films synthesized from glucose (71.75 nm and 87.4°, respectively). Those films performed better as cell scaffolds: the number of viable NIH fibroblasts was 1.7–1.9 times higher than on polystyrene (control) or films of P(3HB) synthesized from glucose.