title: Novel strategy for yeast construction using delta-integration and cell fusion to efficiently produce ethanol from raw starch.
abstract: We developed a novel strategy for constructing yeast to improve levels of amylase gene expression and the practical potential of yeast by combining delta-integration and polyploidization through cell fusion. Streptococcus bovis alpha-amylase and Rhizopus oryzae glucoamylase/alpha-agglutinin fusion protein genes were integrated into haploid yeast strains. Diploid strains were constructed from these haploid strains by mating, and then a tetraploid strain was constructed by cell fusion. The alpha-amylase and glucoamylase activities of the tetraploid strain were increased up to 1.5- and tenfold, respectively, compared with the parental strain. The diploid and tetraploid strains proliferated faster, yielded more cells, and fermented glucose more effectively than the haploid strain. Ethanol productivity from raw starch was improved with increased ploidy; the tetraploid strain consumed 150 g/l of raw starch and produced 70 g/l of ethanol after 72 h of fermentation. Our strategy for constructing yeasts resulted in the simultaneous overexpression of genes integrated into the genome and improvements in the practical potential of yeasts.
authors.affiliation: Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, Nada-ku, Kobe, Hyogo 657-8501, Japan.
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: Hideki
authors.initials: H
authors.lastname: Fukuda
authors.forename: Akihiko
authors.initials: A
authors.lastname: Kondo
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D003001:Cloning, Molecular; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D015966:Gene Expression Regulation, Fungal; D005818:Genetic Engineering; D005087:Glucan 1,4-alpha-Glucosidase / Q000235:genetics* / Q000378:metabolism; D011123:Polyploidy; D011994:Recombinant Proteins / Q000378:metabolism; D012233:Rhizopus / Q000201:enzymology / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D013213:Starch / Q000378:metabolism*; D016985:Streptococcus bovis / Q000201:enzymology / Q000235:genetics; D013379:Substrate Specificity; D014170:Transformation, Genetic; D000516:alpha-Amylases / Q000235:genetics* / Q000378:metabolism
chemical_list: D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D000431:Ethanol; D013213:Starch; D000516:alpha-Amylases; D005087:Glucan 1,4-alpha-Glucosidase