title: Overexpression of the NADP+-specific isocitrate dehydrogenase gene (icdA) in citric acid-producing Aspergillus niger WU-2223L.
abstract: In the tricarboxylic acid (TCA) cycle, NADP(+)-specific isocitrate dehydrogenase (NADP(+)-ICDH) catalyzes oxidative decarboxylation of isocitric acid to form α-ketoglutaric acid with NADP(+) as a cofactor. We constructed an NADP(+)-ICDH gene (icdA)-overexpressing strain (OPI-1) using Aspergillus niger WU-2223L as a host and examined the effects of increase in NADP(+)-ICDH activity on citric acid production. Under citric acid-producing conditions with glucose as the carbon source, the amounts of citric acid produced and glucose consumed by OPI-1 for the 12-d cultivation period decreased by 18.7 and 10.5%, respectively, compared with those by WU-2223L. These results indicate that the amount of citric acid produced by A. niger can be altered with the NADP(+)-ICDH activity. Therefore, NADP(+)-ICDH is an important regulator of citric acid production in the TCA cycle of A. niger. Thus, we propose that the icdA gene is a potentially valuable tool for modulating citric acid production by metabolic engineering.
authors.affiliation: a Faculty of Science and Engineering, Department of Applied Chemistry , Waseda University , Shinjuku-ku , Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Takasumi
authors.initials: T
authors.lastname: Hattori
authors.forename: Rie
authors.initials: R
authors.lastname: Hayashi
authors.forename: Kohtaro
authors.initials: K
authors.lastname: Kirimura
mesh_terms: D001234:Aspergillus niger / Q000166:cytology / Q000235:genetics* / Q000378:metabolism*; D019343:Citric Acid / Q000378:metabolism*; D015870:Gene Expression; D042541:Intracellular Space / Q000378:metabolism; D007521:Isocitrate Dehydrogenase / Q000235:genetics*; D008293:Malates / Q000378:metabolism; D060847:Metabolic Engineering
chemical_list: D008293:Malates; D019343:Citric Acid; C030298:malic acid; D007521:Isocitrate Dehydrogenase; C039355:isocitrate dehydrogenase (NADP+)
keywords: Aspergillus niger; NADP+-isocitrate dehydrogenase; citric acid production; metabolic engineering