| Summary: | 碩士 === 元智大學 === 化學工程與材料科學學系 === 96 === Poly(3-hydroxybutyrate-co-3-mercaptopropinate) (P(3HB-co-3MP)) is a kind of polythioesters (PTE) and is synthesized by a novel root nodule bacterium, Cupriavidus taiwanensis 184, originally isolated from Mimosa sp. in southern Taiwan. A two-stage fermentation method is adapted for the production of the PTE copolymer. A sulfur-containing carbonic acid, 3,3''-thiodipropionic acid (TDPA), is supplied as the second carbon source to form the 3MP component in the PTE copolymer.
Fourier transform infrared spectroscopy (FTIR), gas chromatography/mass spectrometry (GC/MS) and nuclear magnetic resonance spectroscopy (NMR) are applied to confirm the chemical structure of the P(3HB-co-3MP) copolymer. The P(3HB-co-3MP) shows a D value of 0.98 and R value of 1.01. The D value and R value are closed to 1 for all P(3HB-co-3MP) copolymers. It indicates P(3HB-co-3MP) copolymers are random sequence distribution. The sulfur content of the copolymer is determined by NMR and elemental analysis (EA), and it is proportional to the feeding amount of TDPA in the substrate at the second stage and fermentation time.
The P(3HB-co-3MP) copolymer shows multi-melting peaks. The multiple melting peaks indicated the 3MP unit would influence the crystallization of 3HB and form imperfect crystal. Both the crystallization rate and the degree of crystallinity of P(3HB-co-3MP) is lower than those of P3HB due to the presence of 3MP component. The P(3HB-co-3MP) copolymers have small crystallite size and lower crystallinity than P3HB due to addition of 3MP component. There are significant difference of Ti and Tp among the PTEs with various culturing time in the second stage. With longer culturing time, P(3HB-co-3MP) shows better thermal stability than P3HB. Because, the thermal properties of P(3HB-co-3MP) were found to show a strong dependence on the comonomer unit content.
|
|---|
