title: Co-production of hydrogen and ethanol from glucose by modification of glycolytic pathways in Escherichia coli - from Embden-Meyerhof-Parnas pathway to pentose phosphate pathway.
abstract: Hydrogen (H2) production from glucose by dark fermentation suffers from the low yield. As a solution to this problem, co-production of H2 and ethanol, both of which are good biofuels, has been suggested. To this end, using Escherichia coli, activation of pentose phosphate (PP) pathway, which can generate more NADPH than the Embden-Meyhof-Parnas (EMP) pathway, was attempted. Overexpression of two key enzymes in the branch nodes of the glycolytic pathway, Zwf and Gnd, significantly improved the co-production of H2 and ethanol with concomitant reduction of pyruvate secretion. Gene expression analysis and metabolic flux analysis (MFA) showed that, upon overexpression of Zwf and Gnd, glucose assimilation through the PP pathway, compared with that of the EMP or Entner-Doudoroff (ED) pathway, was greatly enhanced. The maximum co-production yields were 1.32 mol H2 mol(-1) glucose and 1.38 mol ethanol mol(-1) glucose, respectively. It is noteworthy that the glycolysis and the amount of NAD(P)H formed under anaerobic conditions could be altered by modifying (the activity of) several key enzymes. Our strategy could be applied for the development of industrial strains for biological production of reduced chemicals and biofuels which suffers from lack of reduced co-factors.
authors.affiliation: Department of Chemical and Biomolecular Engineering, Pusan National University, Busan, Republic of Korea.
authors.forename: Eunhee
authors.initials: E
authors.lastname: Seol
authors.affiliation: Department of Chemical and Biomolecular Engineering, Pusan National University, Busan, Republic of Korea.
authors.forename: Balaji Sundara
authors.initials: BS
authors.lastname: Sekar
authors.affiliation: Centre for Research and Development, PRIST University, Thanjavur, India.
authors.forename: Subramanian Mohan
authors.initials: SM
authors.lastname: Raj
authors.affiliation: Department of Chemical and Biomolecular Engineering, Pusan National University, Busan, Republic of Korea. parksh@pusan.ac.kr.
authors.forename: Sunghoon
authors.initials: S
authors.lastname: Park
mesh_terms: D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development; D029968:Escherichia coli Proteins / Q000235:genetics; D000431:Ethanol / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D006019:Glycolysis; D006859:Hydrogen / Q000378:metabolism*; D060847:Metabolic Engineering; D010427:Pentose Phosphate Pathway
chemical_list: D029968:Escherichia coli Proteins; D000431:Ethanol; D006859:Hydrogen; D005947:Glucose
keywords: Escherichia coli; NAD(P)H generation; co-production of hydrogen and ethanol; pentose phosphate pathway; pfkA deletion