title: Repeated batch fermentation from raw starch using a maltose transporter and amylase expressing diploid yeast strain.
abstract: We successfully demonstrated batch ethanol fermentation repeated ten times from raw starch with high ethanol productivity. We constructed a yeast diploid strain coexpressing the maltose transporter AGT1, alpha-amylase, and glucoamylase. The introduction of AGT1 allows maltose and maltotriose fermentation as well as the improvement of amylase activities. We also found that alpha-amylase activity during fermentation was retained by the addition of 10 mM calcium ion and that the highest alpha-amylase activity was 9.26 U/ml during repeated fermentation. The highest ethanol productivity was 2.22 g/l/h at the fourth batch, and after ten cycles, ethanol productivity of more than 1.43 g/l/h was retained, as was alpha-amylase activity at 6.43 U/ml.
authors.affiliation: Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodaicho, Nada-ku, Kobe, Hyogo 657-8501, Japan.
authors.forename: Syun-ichi
authors.initials: S
authors.lastname: Yamakawa
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Yamada
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Tanaka
authors.forename: Chiaki
authors.initials: C
authors.lastname: Ogino
authors.forename: Akihiko
authors.initials: A
authors.lastname: Kondo
mesh_terms: D000681:Amylases / Q000235:genetics / Q000378:metabolism*; D018533:Biomass; D019149:Bioreactors / Q000382:microbiology*; D004171:Diploidy; D000431:Ethanol; D005285:Fermentation; D015870:Gene Expression; D005087:Glucan 1,4-alpha-Glucosidase / Q000235:genetics / Q000378:metabolism; D008320:Maltose / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D013213:Starch / Q000378:metabolism*; D027981:Symporters / Q000235:genetics / Q000378:metabolism*
chemical_list: D009004:Monosaccharide Transport Proteins; D029701:Saccharomyces cerevisiae Proteins; D027981:Symporters; C067575:maltose transport system, S cerevisiae; D000431:Ethanol; D008320:Maltose; D013213:Starch; D000681:Amylases; D005087:Glucan 1,4-alpha-Glucosidase