title: Genetic engineering to enhance the Ehrlich pathway and alter carbon flux for increased isobutanol production from glucose by Saccharomyces cerevisiae.
abstract: The production of higher alcohols by engineered bacteria has received significant attention. The budding yeast, Saccharomyces cerevisiae, has considerable potential as a producer of higher alcohols because of its capacity to naturally fabricate fusel alcohols, in addition to its robustness and tolerance to low pH. However, because its natural productivity is not significant, we considered a strategy of genetic engineering to increase production of the branched-chain higher alcohol isobutanol, which is involved in valine biosynthesis. Initially, we overexpressed 2-keto acid decarboxylase (KDC) and alcohol dehydrogenase (ADH) in S. cerevisiae to enhance the endogenous activity of the Ehrlich pathway. We then overexpressed Ilv2, which catalyzes the first step in the valine synthetic pathway, and deleted the PDC1 gene encoding a major pyruvate decarboxylase with the intent of altering the abundant ethanol flux via pyruvate. Through these engineering steps, along with modification of culture conditions, the isobutanol titer of S. cerevisiae was elevated 13-fold, from 11 mg/l to 143 mg/l, and the yield was 6.6 mg/g glucose, which is higher than any previously reported value for S. cerevisiae.
authors.affiliation: Organization of Advanced Science and Technology, Kobe University, 1-1 Rokkodai, Nada, Kobe, Japan. t-kondo@ynu.ac.jp
authors.forename: Takashi
authors.initials: T
authors.lastname: Kondo
authors.forename: Hironori
authors.initials: H
authors.lastname: Tezuka
authors.forename: Jun
authors.initials: J
authors.lastname: Ishii
authors.forename: Fumio
authors.initials: F
authors.lastname: Matsuda
authors.forename: Chiaki
authors.initials: C
authors.lastname: Ogino
authors.forename: Akihiko
authors.initials: A
authors.lastname: Kondo
mesh_terms: D000332:Aerobiosis; D000426:Alcohol Dehydrogenase / Q000235:genetics / Q000378:metabolism; D000440:Butanols / Q000032:analysis / Q000378:metabolism*; D002244:Carbon / Q000378:metabolism*; D002262:Carboxy-Lyases / Q000235:genetics / Q000378:metabolism; D000431:Ethanol / Q000032:analysis / Q000378:metabolism; D005285:Fermentation; D005818:Genetic Engineering / Q000379:methods*; D005947:Glucose / Q000378:metabolism*; D006836:Hydro-Lyases / Q000235:genetics / Q000378:metabolism; D053858:Metabolic Networks and Pathways / Q000235:genetics; D011767:Pyruvate Decarboxylase / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D000440:Butanols; D029701:Saccharomyces cerevisiae Proteins; D000431:Ethanol; C040507:isobutyl alcohol; D002244:Carbon; D000426:Alcohol Dehydrogenase; D002262:Carboxy-Lyases; C101504:PDC1 protein, S cerevisiae; D011767:Pyruvate Decarboxylase; D006836:Hydro-Lyases; D005947:Glucose