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Effects of Intracellular Redox Level on Fermentation Metabolism of Thermoanaerobacter ethanolicus |
SUN Huan-min, GUO Min, IRBIS Cha-gan |
Laboratory of Bio-conversion, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming 650500, China |
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Abstract Coenzyme NADH/NAD+ plays an important role in intracellular oxidation-reduction reactions, and is a necessary cofactor for cell growth and energy metabolism. Regulating the intracellular NADH/NAD+ ratio of microorganisms is an effective means to alter microbial metabolic pathway directionally and obtain the target metabolic products efficiently. Thermoanaerobacter ethanolicus is a representative thermophilic anaerobic and ethanologenic bacteria. This study altered intracellular NADH/NAD+ ratio using carbon sources at different redox status. Then its effect on cell growth and distribution of metabolic products was studied. When glucose and mannitol at different ratios were used as the substrate for fermentation, variations occurred with respect to intracellular redox level, growth characteristics of cells and metabolic products. When glucose was used as the only carbon source, T. ethanolicus grew well, and the ethanol production was 0.79g/L. However, both of the intracellular NADH/NAD+ ratio and ethanol/acetic acid ratio were low, being 0.474 and 4.82 respectively. As the ratio of glucose in the mixed carbon source decreased, the NADH/NAD+ ratio increased, and the ethanol/acetic acid ratio in the fermentation products also showed an increasing trend. When mannitol was used as the only carbon source, the ethanol concentration in the fermentation products was 0.389g/L, and the NADH/NAD+ ratio and ethanol/acetic acid ratio were 1.04 and 16.0 respectively.
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Received: 11 May 2012
Published: 25 July 2012
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[1] Grazina M, Silva F, Januario C, et al. Parkinson's disease and mitochondrial DNA NADH dehydrogenase subunit 1 nucleotides 3337-3340: study in a population from the central region of Portugal (Coimbra). Eur Neurol, 2003, 50(1): 60-61. [2] St Clair N, Wang Y F, Margolin A L. Cofactor-Bound Cross-Linked Enzyme Crystals (CLEC) of Alcohol Dehydrogenase. Angew Chem Int Ed Engl, 2000, 39(2): 380-383. [3] Leonardo M R, Cunningham P R, Clark D P. Anaerobic regulation of the adhE gene, encoding the fermentative alcohol dehydrogenase of Escherichia coli. J Bacteriol, 1993, 175(3): 870-878. [4] de Graef M R, Alexeeva S, Snoep J L, et al. The steady-state internal redox state (NADH/NAD) reflects the external redox state and is correlated with catabolic adaptation in Escherichia coli. J Bacteriol, 1999, 181(8): 2351-2357. [5] Leonardo M R, Dailly Y, Clark D P. Role of NAD in regulating the adhE gene of Escherichia coli. J Bacteriol, 1996, 178(20): 6013-6018. [6] Alam K Y, Clark D P. Anaerobic fermentation balance of Escherichia coli as observed by in vivo nuclear magnetic resonance spectroscopy. J Bacteriol, 1989, 171(11): 6213-6217. [7] Girbal L,Soucaille P. Regulation of Clostridium acetobutylicum metabolism as revealed by mid-substrate steady state continous cultures:role of NADH/ NAD+ ratio and ATP pool.Bacteriol,1994,176(21):6433-6438. [8] Vane L M, Alvarez F R. Membrane-assisted vapor stripping: energy efficient hybrid distillation-vapor permeation process for alcohol-water separation. Journal of Chemical Technology and Biotechnology, 2008, 83(9): 1275-1287. [9] Sommer P, Georgieva T, Ahring B K. Potential for using thermophilic anaerobic bacteria for bioethanol production from hemicellulose. Biochem Soc Trans, 2004, 32(2): 283-289. [10] Zaldivar J, Nielsen J, Olsson L. Fuel ethanol production from lignocellulose: a challenge for metabolic engineering and process integration. Appl Microbiol Biotechnol, 2001, 56(1-2): 17-34. [11] Peng J J, Zhou Q, Jing Q Q, et al. The mechanism for regulating ethanol fermentation by redox levels in Thermoanaerobacter ethanolicus.Metabolic Engineering,2011,13(2):186-193. [12] Kataoka M, Rohani L P, Yamamoto K, et al. Enzymatic production of ethyl (R)-4-chloro-3-hydroxybutanoate: asymmetric reduction of ethyl 4-chloro-3-oxobutanoate by an Escherichia coli transformant expressing the aldehyde reductase gene from yeast. Appl Microbiol Biotechnol, 1997, 48(6): 699-703. [13] 王庆昭.高产琥珀酸大肠杆菌的代谢工程. 天津:天津大学,化工学院,2006. Wang Q Z. Metabolic engineering of Escherichia coli for improved succinic acid production. Tianjin:Tianjin University, Chemical Engineering Institute,2006. [14] San K Y, Bennett, G N, Berrios-Rivera S J, et al. Metabolic engineering through cofactor manipulation and its effects on metabolic flux redistribution in Escherichia coli. Metab Eng, 2002, 4 (2): 182-192. [15] Lin H, Bennett G N, San K Y. Effect of carbon sources differing in oxidation state and transport route on succinate production in metabolically engineered Escherichia coli. J Ind Microbiol Biotechnol, 2005,32 (3): 87-93. |
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