title: An improved stereoselective reduction of a bicyclic diketone by Saccharomyces cerevisiae combining process optimization and strain engineering.
abstract: The stereoselective reduction of the bicyclic diketone bicyclo[2.2.2]octane-2,6-dione, to the ketoalcohol (1R,4S,6S)-6-hydroxybicyclo[2.2.2]octane-2-one, was used as a model reduction to optimize parameters involved in NADPH-dependent reductions in Saccharomyces cerevisiae with glucose as co-substrate. The co-substrate yield (ketoalcohol formed/glucose consumed) was affected by the initial concentration of bicyclic diketone, the ratio of yeast to glucose, the medium composition, and the pH. The reduction of 5 g l(-1) bicyclic diketone was completed in less than 20 h in complex medium (pH 5.5) under oxygen limitation with an initial concentration of 200 g l(-1) glucose and 5 g l(-1) yeast. The co-substrate yield was further enhanced by genetically engineered strains with reduced phosphoglucose isomerase activity and with the gene encoding alcohol dehydrogenase deleted. Co-substrate yields were increased 2.3-fold and 2.4-fold, respectively, in these strains.
authors.affiliation: Department of Applied Microbiology, Lund University, PO Box 124, 22100 Lund, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Katz
authors.forename: I
authors.initials: I
authors.lastname: Sarvary
authors.forename: T
authors.initials: T
authors.lastname: Frejd
authors.forename: B
authors.initials: B
authors.lastname: Hahn-Hägerdal
authors.forename: M F
authors.initials: MF
authors.lastname: Gorwa-Grauslund
mesh_terms: D000426:Alcohol Dehydrogenase / Q000235:genetics / Q000378:metabolism; D000438:Alcohols / Q000378:metabolism*; D001643:Bridged Bicyclo Compounds / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D005956:Glucose-6-Phosphate Isomerase / Q000235:genetics / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007659:Ketones / Q000378:metabolism*; D030781:Organisms, Genetically Modified; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*
chemical_list: D000438:Alcohols; D001643:Bridged Bicyclo Compounds; D007659:Ketones; D000426:Alcohol Dehydrogenase; D005956:Glucose-6-Phosphate Isomerase; D005947:Glucose