title: Engineering the pentose phosphate pathway to improve hydrogen yield in recombinant Escherichia coli.
abstract: Among various routes for the biological hydrogen production, the NAD(P)H-dependent pentose phosphate (PP) pathway is the most efficient for the dark fermentation. Few studies, however, have focused on the glucose-6-phosphate 1-dehydrogenase, encoded by zwf, as a key enzyme activating the PP pathway. Although the gluconeogenic activity is essential for activating the PP pathway, it is difficult to enhance the NADPH production by regulating only this activity because the gluconeogenesis is robust and highly sensitive to concentrations of glucose and AMP inside the cell. In this study, the FBPase II (encoded by glpX), a regulation-insensitive enzyme in the gluconeogenic pathway, was activated. Physiological studies of several recombinant, ferredoxin-dependent hydrogenase system-containing Escherichia coli BL21(DE3) strains showed that overexpression of glpX alone could increase the hydrogen yield by 1.48-fold compared to a strain with the ferredoxin-dependent hydrogenase system only; the co-overexpression of glpX with zwf increased the hydrogen yield further to 2.32-fold. These results indicate that activation of the PP pathway by glpX overexpression-enhanced gluconeogenic flux is crucial for the increase of NAD(P)H-dependent hydrogen production in E. coli BL21(DE3).
authors: School of Environmental Science and Engineering, Pohang University of Science and Technology, San 31, Hyoja-Dong, Pohang 790-784, Korea.
authors: Young Mi
authors: YM
authors: Kim
authors: Han-Saem
authors: HS
authors: Cho
authors: Gyoo Yeol
authors: GY
authors: Jung
authors: Jong Moon
authors: JM
authors: Park
mesh_terms: D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D005285:Fermentation; D006597:Fructose-Bisphosphatase / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D005818:Genetic Engineering; D005954:Glucosephosphate Dehydrogenase / Q000235:genetics / Q000378:metabolism; D006859:Hydrogen / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D030781:Organisms, Genetically Modified / Q000235:genetics / Q000378:metabolism*; D010427:Pentose Phosphate Pathway / Q000235:genetics*
chemical_list: D029968:Escherichia coli Proteins; C077563:GlpX protein, E coli; D009249:NADP; D006859:Hydrogen; D005954:Glucosephosphate Dehydrogenase; D006597:Fructose-Bisphosphatase