Biosynthesis and characterization of novel polyhydroxyalkanoate by cupriavidus necator phb-4 transformant harboring pha synthase gene of chromobacterium sp. USM2
| dc.contributor.author | Tin Fong, Ooi | |
| dc.date.accessioned | 2015-05-06T07:31:52Z | |
| dc.date.available | 2015-05-06T07:31:52Z | |
| dc.date.issued | 2011 | |
| dc.description.abstract | The incorporation of a newly identified 3-hydroxy-4-methylvalerate (3H4MV) monomer into the backbone of polyhydroxyalkanoate (PHA) is thought to improve the properties of the resulting polymer. In this study, a transformant of C. necator PHB-4 harboring the PHA synthase gene of Chromobacterium sp. USM2 [CO - necator PHB 4 (PhaCcs)] was evaluated for its ability to synthesize novel short-chain and medium-chain-Iength (SCL-MCL) PHA containing 3H4MV. Fructose or crude palm kernel oil (CPKO) was used as main carbon source together with isocaproic acid (4MV) as precursor to produce the excellent SCL-MCL PHA. 4MV concentration and its feeding time had been identified as important parameters affecting PHA content and monomer composition of the resulting polymer. A novel PHA that consists of 78 mol % 3HB, 1 mol % 3HV, 3 mol % 3H4MV and 18 mol % 3HHx was obtained when 5 gIL CPKO and 1 gIL 4MV were fed during initial inoculation. This PHA has a very interesting characteristic - rubber-like character even after one year of aging. It can retract after being released from the stretching. This property has not been found in any of the previously reported PHA. Another transformant of C. necator PHB-4 harboring the PHA synthase gene of Aeromonas caviae [CO necator PHB 4 (phaCAc)] was used as well for comparison of its ability to produce PHA that contained different monomer compositions of 3H4MV. The novel SCL-MCL PHA that was produced by C. necator PHB 4 (phaCcs) was characterized '\ to further understand its excellent properties. Structural characterizations were carried out by IH NMR and 13C NMR spectroscopes while FT-IR was done to confirm the presence of the functional groups of PHA. Besides, thermal properties determined by TGA and DSC to compare these SCL-MCL PHA with P(3HB-co- 3HHx) copolymer showed that the incorporation of 3H4MV monomer and enhanced 3HHx monomer composition in the PHA have lowered the Tg, T m and Mm. The molecular weights of the polymers were in the range of 7 - 10 x 105 • Mechanical tests were also carried out. The tensile strength was in the range of 15 - 27 MPa, Young's modulus in the range of 84 - 623 MPa and elongation at break in the range of 84 - 478 %. Application of fine PHA fiber was successfully fabricated using an electro spinning machine with controlled parameters. Besides, degradation of the SCL-MCL PHA film done on the surface of soil showed that it degraded faster compared to P(3HB) and P(3HB-co-3HHx) films. | en_US |
| dc.identifier.uri | http://hdl.handle.net/123456789/608 | |
| dc.language.iso | en | en_US |
| dc.title | Biosynthesis and characterization of novel polyhydroxyalkanoate by cupriavidus necator phb-4 transformant harboring pha synthase gene of chromobacterium sp. USM2 | en_US |
| dc.type | Thesis | en_US |
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