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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
Author(s) -
Seol Eunhee,
Sekar Balaji Sundara,
Raj Subramanian Mohan,
Park Sunghoon
Publication year - 2016
Publication title -
biotechnology journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.144
H-Index - 84
eISSN - 1860-7314
pISSN - 1860-6768
DOI - 10.1002/biot.201400829
Subject(s) - pentose phosphate pathway , glycolysis , biochemistry , fermentation , chemistry , metabolic pathway , nad+ kinase , ethanol , ethanol fuel , escherichia coli , enzyme , zymomonas mobilis , metabolic engineering , gene
Hydrogen (H 2 ) production from glucose by dark fermentation suffers from the low yield. As a solution to this problem, co‐production of H 2 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 H 2 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 H 2 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.