Dual biosyntheses of poly[(R)-3-hydroxybutyric acid] and silk protein for the fabrication of biofunctional bioplastic

This is the first report on dual synthesis of poly[(R)-3-hydroxybutyric acid] (PHB) and protein polymer by recombinant microorganisms for use in the fabrication of a biofunctional PHB-based material hybridized with functional proteins. PHB and recombinant silk protein, a model protein developed in this study, were synthesized by a recombinant Escherichia coli system, and then films of PHB hybridized with the silk protein (PHB/Silk) were prepared. The presence of the silk protein in the amorphous phase of the PHB/Silk film was demonstrated based on wide-angle X-ray diffraction and differential scanning calorimetry measurements, which also revealed the enhanced tensile strength and elongation at break of the PHB/Silk film. The cell adhesion of human mesenchymal stem cells (hMSCs) for the PHB/Silk film increased because of the addition of silk molecules to the film. This might have been because the silk molecules existed in the amorphous phase at the surface of the PHB/Silk films, and were exposed to hMSCs. The overall results illustrate the potential of this dual synthesis system as a versatile and useful platform method for preparation of biofunctional PHB-based materials, especially for biomedical applications. Polymer Journal (2011) 43, 642–647; doi:10.1038/pj.2011.27; published online 27 April 2011