title: Evaluation of performance of different surface-engineered yeast strains for direct ethanol production from raw starch.
abstract: 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.
authors.affiliation: Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
authors.forename: Teik Seong
authors.initials: TS
authors.lastname: Khaw
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Katakura
authors.forename: Jun
authors.initials: J
authors.lastname: Koh
authors.forename: Akihiko
authors.initials: A
authors.lastname: Kondo
authors.forename: Mitsuyoshi
authors.initials: M
authors.lastname: Ueda
authors.forename: Suteaki
authors.initials: S
authors.lastname: Shioya
mesh_terms: D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D015870:Gene Expression; D005818:Genetic Engineering; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D013213:Starch / Q000378:metabolism*; D000516:alpha-Amylases / Q000235:genetics / Q000378:metabolism
chemical_list: D000431:Ethanol; D013213:Starch; D000516:alpha-Amylases