| Summary: | 碩士 === 國立交通大學 === 分子醫學與生物工程研究所 === 102 === Biofuel synthesis is of increasing interest because of global energy and environmental problems. Isobutanol is a renewable and clean biofuel. Compared with ethanol, isobutanol has high energy density to burn, low corrosiveness to be stored and long carbon chain, which is similar to gasoline. Furthermore, isobutanol can completely replace gasoline without engine modification. Since Escherichia coli can broadly utilize 5-C sugar (xylose, arabinose, mannose) and 6-C sugar (glucose, galactose); therefore, it is a promising host to produce isobutanol. In this study, four genes (alsS, ilvC, ilvD, kivd) were cloned and transformed into E. coli DH5α to direct glycolysis pathway for isobutanol production. In order to improve the yield of isobutanol, a thermo- sensitive ribosome biding site and tetR repressor were used to repress kivd gene expression and overcome the barrier of isobutanol tolerance of E. coli. The result revealed that E. coli harboring four genes overexpression could produce 0.4 g/L (v/v) isobutanol after 48 h cultivation. Moreover, E. coli harboring the modified plasmid with temperature control could achieve 20 g/L isobutanol yield. This result indicates that thermo-sensitive RBS for expressing kivd gene in E. coli may enhance isobutanol production by temperature.
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