| Summary: | 碩士 === 明志科技大學 === 化學工程系生化工程碩士班 === 102 === Aliphatic α,ω-dicarboxylic acids (DCA) of the type addressed by this program are used in a wide variety of plastics and other chemical applications. The DCA12 produced in the largest quantity (>40 MM lb/yr) as a pure chemical intermediate is dodecanedioic acid (C12); it is used in polyamides such as nylon 6,12, which is noted for high moisture resistance. The dodecanedioic process is based on non-renewable petrochemical feedstocks. The multi-step conversion process produces unwanted byproducts such as cyclooctadiene and vinyl cyclohexene, which result in yield losses. The nitric acid oxidation step yields NOx, which is either released to the atmosphere or must be destroyed in a reduction furnace. Biotechnology offers an innovative way to overcome the limitations and disadvantages of the chemical processes to make diacids. Yarrowia biocatalyst we constructed are able to convert long-chain fatty acids directly to cost-competitive long-chain dodecanedioic acid through overexpressing ω-oxidation pathway and blocking the β-oxidation pathway. In this research, Four genes (Cytochrome P450 monxygenase, Cytochrome P450 NADPH reductase, Fatty alcohol oxidase, and Fatty aldehyde dehydrogenase) were selected to increase the rate of conversion of fatty acid in ω-oxidation pathway and deletions strain(pox2) were also constructed. Our results demonstrated that fatty acid production in the pox2 deletion strain enhance about 20 wt % which overexpress the ω-oxidation pathway genes can enhance DCA12 production. This research were to increase the rate of conversion of glucose into the corresponding fatty acid feedstocks through overexpressing of the gene of fatty acid synthesis, Acetyl-CoA carboxylase (AccD) and Fatty acid synthase (FA-1, FA-2, FB-1), in Yarrowia biocatalyst. In order to enhance DCA12 content, the Yarrowia-codon acyl-carrier protein thioesterase gene, BTE from Umbellularia califoenica, FatB3 from Cocos nucifera were also expressed. The results demonstrated that expressed BTE and FatB3 can enhance DCA12 from 12.9% to 51.2%. Finally, the RNA inference technology and pH-controlled fermentation were also used to enhance DCA12 production, the yield from 2.35 g/L to 112.05 g/L.
|
|---|
