title: Inhibition of oxidative phosphorylation for enhancing citric acid production by Aspergillus niger.
abstract: BACKGROUND
  The spore germination rate and growth characteristics were compared between the citric acid high-yield strain Aspergillus niger CGMCC 5751 and A. niger ATCC 1015 in media containing antimycin A or DNP. We inferred that differences in citric acid yield might be due to differences in energy metabolism between these strains. To explore the impact of energy metabolism on citric acid production, the changes in intracellular ATP, NADH and NADH/NAD+ were measured at various fermentation stages. In addition, the effects of antimycin A or DNP on energy metabolism and citric acid production was investigated by CGMCC 5751.
  
  
  RESULTS
  By comparing the spore germination rate and the extent of growth on PDA plates containing antimycin A or DNP, CGMCC 5751 was shown to be more sensitive to antimycin A than ATCC 1015. The substrate-level phosphorylation of CGMCC 5751 was greater than that of ATCC 1015 on PDA plates with DNP. DNP at tested concentrations had no apparent effect on the growth of CGMCC 5751. There were no apparent effects on the mycelial morphology, the growth of mycelial pellets or the dry cell mass when 0.2 mg L(-1) antimycin A or 0.1 mg L(-1) DNP was added to medium at the 24-h time point. The concentrations of intracellular ATP, NADH and NADH/NAD+ of CGMCC 5751 were notably lower than those of ATCC 1015 at several fermentation stages. Moreover, at 96 h of fermentation, the citric acid production of CGMCC 5751 reached up to 151.67 g L(-1) and 135.78 g L(-1) by adding 0.2 mg L(-1) antimycin A or 0.1 mg L(-1) DNP, respectively, at the 24-h time point of fermentation. Thus, the citric acid production of CGMCC 5751 was increased by 19.89% and 7.32%, respectively.
  
  
  CONCLUSIONS
  The concentrations of intracellular ATP, NADH and NADH/NAD+ of the citric acid high-yield strain CGMCC 5751 were notably lower than those of ATCC 1015. The excessive ATP has a strong inhibitory effect on citric acid accumulation by A. niger. Increasing NADH oxidation and appropriately reducing the concentration of intracellular ATP can accelerate glycolysis and the TCA cycle to enhance citric acid yield.
authors.affiliation: Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin, 300457, P. R. China. 294979404@qq.com.|College of Biotechnology, Tianjin University of Science & Technology, Tianjin, 300457, P. R. China. 294979404@qq.com.
authors.forename: Lu
authors.initials: L
authors.lastname: Wang
authors.affiliation: Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin, 300457, P. R. China. 1244773958@qq.com.|College of Biotechnology, Tianjin University of Science & Technology, Tianjin, 300457, P. R. China. 1244773958@qq.com.
authors.forename: Jianhua
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin, 300457, P. R. China. 378838700@qq.com.|College of Biotechnology, Tianjin University of Science & Technology, Tianjin, 300457, P. R. China. 378838700@qq.com.
authors.forename: Zhanglei
authors.initials: Z
authors.lastname: Cao
authors.affiliation: Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin, 300457, P. R. China. yajun54521@qq.com.|College of Biotechnology, Tianjin University of Science & Technology, Tianjin, 300457, P. R. China. yajun54521@qq.com.
authors.forename: Yajun
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin, 300457, P. R. China. 907399968@qq.com.|College of Biotechnology, Tianjin University of Science & Technology, Tianjin, 300457, P. R. China. 907399968@qq.com.|Tianjin Key Laboratory of Industrial Microbiology, Tianjin, 300457, P. R. China. 907399968@qq.com.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Gao
authors.affiliation: Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin, 300457, P. R. China. zj96sk@tust.edu.com.|College of Biotechnology, Tianjin University of Science & Technology, Tianjin, 300457, P. R. China. zj96sk@tust.edu.com.|Tianjin Key Laboratory of Industrial Microbiology, Tianjin, 300457, P. R. China. zj96sk@tust.edu.com.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin, 300457, P. R. China. shiyao218@163.com.|College of Biotechnology, Tianjin University of Science & Technology, Tianjin, 300457, P. R. China. shiyao218@163.com.|Tianjin Key Laboratory of Industrial Microbiology, Tianjin, 300457, P. R. China. shiyao218@163.com.
authors.forename: Depei
authors.initials: D
authors.lastname: Wang
mesh_terms: D019297:2,4-Dinitrophenol / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000968:Antimycin A / Q000494:pharmacology; D001234:Aspergillus niger / Q000502:physiology*; D019343:Citric Acid / Q000378:metabolism*; D004734:Energy Metabolism; D009243:NAD / Q000378:metabolism; D010085:Oxidative Phosphorylation / Q000187:drug effects; D013172:Spores, Fungal / Q000187:drug effects / Q000254:growth & development
chemical_list: D009243:NAD; D019343:Citric Acid; D000968:Antimycin A; D000255:Adenosine Triphosphate; D019297:2,4-Dinitrophenol