title: Utilization of excess NADH in 2,3-butanediol-deficient Klebsiella pneumoniae for 1,3-propanediol production.
abstract: OBJECTIVE
  To utilize excess NADH for 1,3-propanediol production by 2,3-butanediol-deficient mutants, the effect of dhaT overexpression in two distinct 2,3-butanediol-deficient mutants was investigated.
  
  
  RESULTS
  Two 2,3-butanediol-deficient mutants, KG1-3 (blocking of the 2,3-butanediol pathway only) and KG1-5 (blocking of both of 2,3-butanediol and lactate pathways) were constructed. Our results showed that although the intracellular redox balance (NADH/NAD(+)) was extremely high at the end of fermentation for both mutants, the status of intracellular redox in KG1-5 was maintained at a normal level following the first stage of fermentation. Analysis of cell growth and metabolite formation confirmed the inhibition of excess lactate in 2,3-butanediol pathway-deficient mutants. Furthermore, dhaT was overexpressed in two 2,3-butanediol-deficient mutants (KG1-3T and KG1-5T). In KG1-5T, the intracellular redox balance was restored to normal and 1,3-propanediol production increased. The yield of 1,3-propanediol from glycerol in KG1-5T was also restored to a normal level of 0·6.
  
  
  CONCLUSIONS
  The excess NADH in both the 2,3-butanediol- and lactate-deficient mutants can be used by overexpresstion of dhaT.
  
  
  CONCLUSIONS
  The metabolic flux tended to increase lactate production by the abolishment of the 2,3-butanediol pathway in Klebsiella pneumoniae, and the high accumulation of lactate prevented the cell from using excess NADH, thereby inhibiting cell growth and 1,3-propanediol production.
authors: State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, China.
authors: Y L
authors: YL
authors: Cui
authors: J J
authors: JJ
authors: Zhou
authors: L R
authors: LR
authors: Gao
authors: C Q
authors: CQ
authors: Zhu
authors: X
authors: X
authors: Jiang
authors: S L
authors: SL
authors: Fu
authors: H
authors: H
authors: Gong
mesh_terms: D000426:Alcohol Dehydrogenase / Q000235:genetics / Q000378:metabolism; D002072:Butylene Glycols / Q000378:metabolism*; D005285:Fermentation; D005990:Glycerol / Q000378:metabolism; D007711:Klebsiella pneumoniae / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D019344:Lactic Acid / Q000378:metabolism; D009154:Mutation; D009243:NAD / Q000378:metabolism*; D011409:Propylene Glycols / Q000378:metabolism*
chemical_list: D002072:Butylene Glycols; D011409:Propylene Glycols; D009243:NAD; D019344:Lactic Acid; C026978:2,3-butylene glycol; C041787:1,3-propanediol; D000426:Alcohol Dehydrogenase; C052370:1,3-propanediol dehydrogenase; D005990:Glycerol
keywords: 1,3-propanediol; 2,3-butanediol; Klebsiella pneumoniae; NADH; dhaT overexpression; lactate