Evaluation of performance of different surface-engineered yeast strains for direct ethanol production from raw starch.
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.
Khaw
Teik Seong
TS
Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
Katakura
Yoshio
Y
Koh
Jun
J
Kondo
Akihiko
A
Ueda
Mitsuyoshi
M
Shioya
Suteaki
S
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
D000431:Ethanol; D013213:Starch; D000516:alpha-Amylases