title: Construction of a beta-glucosidase expression system using the multistress-tolerant yeast Issatchenkia orientalis.
abstract: We demonstrate the value of the thermotolerant yeast Issatchenkia orientalis as a candidate microorganism for bioethanol production from lignocellulosic biomass with the goal of consolidated bioprocessing. The I. orientalis MF-121 strain is acid tolerant, ethanol tolerant, and thermotolerant, and is thus a multistress-tolerant yeast. To express heterologous proteins in I. orientalis, we constructed a transformation system for the MF-121 strain and then isolated the promoters of TDH1 and PGK1, two genes that were found to be strongly expressed during ethanol fermentation. As a result, expression of beta-glucosidase from Aspergillus aculeatus could be achieved with I. orientalis, demonstrating successful heterologous gene expression in I. orientalis for the first time. The transformant could convert cellobiose to ethanol under acidic conditions and at high temperature. Simultaneous saccharification and fermentation (SSF) was performed with the transformant, which produced 29 g l(-1) of ethanol in 72 h at 40 degrees C even without addition of beta-glucosidase when SSF was carried out in medium containing 100 g l(-1) of microcrystalline cellulose and a commercial cellulase preparation. These results suggest that using a genetically engineered thermotolerant yeast such as I. orientalis in SSF could lead to cost reduction because less saccharification enzymes are required.
authors.affiliation: Department of Applied Molecular Bioscience, Yamaguchi University Graduate School of Medicine, 2-16-1, Tokiwadai, Ube 755-8611, Japan. e1432@mosk.tytlabs.co.jp
authors.forename: Takao
authors.initials: T
authors.lastname: Kitagawa
authors.forename: Kenro
authors.initials: K
authors.lastname: Tokuhiro
authors.forename: Hidehiko
authors.initials: H
authors.lastname: Sugiyama
authors.forename: Katsuhiro
authors.initials: K
authors.lastname: Kohda
authors.forename: Naoto
authors.initials: N
authors.lastname: Isono
authors.forename: Makoto
authors.initials: M
authors.lastname: Hisamatsu
authors.forename: Haruo
authors.initials: H
authors.lastname: Takahashi
authors.forename: Takao
authors.initials: T
authors.lastname: Imaeda
mesh_terms: D000143:Acids / Q000633:toxicity; D001230:Aspergillus / Q000201:enzymology / Q000235:genetics; D002475:Cellobiose / Q000378:metabolism; D000431:Ethanol / Q000378:metabolism; D015870:Gene Expression; D005822:Genetic Vectors; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013696:Temperature; D014170:Transformation, Genetic; D015003:Yeasts / Q000235:genetics* / Q000378:metabolism*; D001617:beta-Glucosidase / Q000235:genetics / Q000378:metabolism*
chemical_list: D000143:Acids; D011994:Recombinant Proteins; D002475:Cellobiose; D000431:Ethanol; D001617:beta-Glucosidase