Khaw Teik Seong, Katakura Yoshio, Koh Jun, Kondo Akihiko, Ueda Mitsuyoshi, Shioya Suteaki
Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
Appl Microbiol Biotechnol. 2006 May;70(5):573-9. doi: 10.1007/s00253-005-0101-z. Epub 2005 Aug 18.
Four types of cell-surface-engineered yeast Saccharomyces cerevisiae displaying glucoamylase, namely, systems A, B, C, and D, were constructed to evaluate their performance in direct ethanol fermentation from raw corn starch. Systems A and B were glucoamylase-displaying nonflocculent yeast (YF237) types that secrete alpha-amylase into the culture medium and codisplay alpha-amylase on the cell surface, respectively. Systems C and D were flocculent yeast counterparts (YF207) for systems A and B, respectively. In batch fermentations, the specific ethanol production rates of systems A, B, C, and D were 0.18, 0.06, 0.06, and 0.04 g (g cell)(-1) h(-1), respectively. In repeated fermentations, the specific ethanol production rate of system A decreased with the number of repetitions, whereas, that of system B was maintained. In all systems, the rate-limiting step was the conversion of starch to oligosaccharide because oligosaccharide and glucose were not accumulated throughout the fermentations.
构建了四种展示糖化酶的细胞表面工程化酿酒酵母，即系统A、B、C和D，以评估它们在从玉米原淀粉直接发酵生产乙醇中的性能。系统A和B是展示糖化酶的非絮凝酵母（YF237）类型，分别向培养基中分泌α-淀粉酶并在细胞表面共展示α-淀粉酶。系统C和D分别是系统A和B的絮凝酵母对应物（YF207）。在分批发酵中，系统A、B、C和D的乙醇比生产率分别为0.18、0.06、0.06和0.04 g（g细胞）-1 h-1。在重复发酵中，系统A的乙醇比生产率随重复次数的增加而降低，而系统B的乙醇比生产率保持不变。在所有系统中，限速步骤是淀粉转化为寡糖，因为在整个发酵过程中寡糖和葡萄糖都没有积累。
