| Summary: | 碩士 === 元智大學 === 生物科技與工程研究所 === 99 === The yeast Saccharomyces cerevisiae is the most commonly used microorganism in traditional industrial fermentations. Although Saccharomyces cerevisiae is suitable for ethanol fermentation, it is unable to metabolize pentose (such as xylose); therefore, the resources used for ethanol fermentation are limited. For the lignocellulose material into fuel ethanol, there will be waste the extra carbon source. In this study, we were using metabolic engineering to improve ability of xylose utilization. Therefore, in this study, we have successfully cloned the pentose utilization genes (XYL1, XYL2 and XKS1) from Pichia stipitis and Saccharomyces cerevisiae into Saccharomyces cerevisiae Hansen BY4742 and Saccharomyces cerevisiae Hansen BY4742 Δzwf1 for biosynthesis of bioethanol. Data shown that the Saccharomyces cerevisiae Hansen BY4742-X3 and Saccharomyces cerevisiae Hansen BY4742 Δzwf1-X3 has mRNA expression for XYL1, XYL2, XKS1 by RT-PCR analysis; and also showed XYL1, XYL2, XKS1 protein production by SDS-PAGE. We also found xylose metabolic pathway can be more smooth for the over expression of XKS1 (Xylulokinase) gene. Moreover, the recombinant Saccharomyces cerevisiae Hansen BY4742 Δzwf1-X3 strain was able to synthesize significant concentration of bioethanol (7.6 g/L), compared with the control strain to increased 0.33g/L. The conversion rate of bioethanol also improved to 0.52 g Ethanol/g Sugar-1. Furthermore, the strain Saccharomyces cerevisiae Hansen BY4742 Δzwf1-X3 can obtain the highest bioethanol production (8.42 g/L) after the enrichment of high concentration of xylose.
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