title: Enhanced hydrogen production from formic acid by formate hydrogen lyase-overexpressing Escherichia coli strains.
abstract: Genetic recombination of Escherichia coli in conjunction with process manipulation was employed to elevate the efficiency of hydrogen production in the resultant strain SR13 2 orders of magnitude above that of conventional methods. The formate hydrogen lyase (FHL)-overexpressing strain SR13 was constructed by combining FHL repressor (hycA) inactivation with FHL activator (fhlA) overexpression. Transcription of large-subunit formate dehydrogenase, fdhF, and large-subunit hydrogenase, hycE, in strain SR13 increased 6.5- and 7.0-fold, respectively, compared to the wild-type strain. On its own, this genetic modification effectively resulted in a 2.8-fold increase in hydrogen productivity of SR13 compared to the wild-type strain. Further enhancement of productivity was attained by using a novel method involving the induction of the FHL complex with high-cell-density filling of a reactor under anaerobic conditions. Continuous hydrogen production was achieved by maintaining the reactor concentration of the substrate (free formic acid) under 25 mM. An initial productivity of 23.6 g hydrogen h(-1) liter(-1) (300 liters h(-1) liter(-1) at 37 degrees C) was achieved using strain SR13 at a cell density of 93 g (dry weight) cells/liter. The hydrogen productivity reported in this work has great potential for practical application.
authors.affiliation: Microbiology Research Group, Research Institute of Innovative Technology for the Earth, 9-2 Kizugawadai, Kizu-cho Soraku-gun, Kyoto 619-0292, Japan.
authors.forename: Akihito
authors.initials: A
authors.lastname: Yoshida
authors.forename: Taku
authors.initials: T
authors.lastname: Nishimura
authors.forename: Hideo
authors.initials: H
authors.lastname: Kawaguchi
authors.forename: Masayuki
authors.initials: M
authors.lastname: Inui
authors.forename: Hideaki
authors.initials: H
authors.lastname: Yukawa
mesh_terms: D001709:Biotechnology / Q000379:methods; D048168:Escherichia coli K12 / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D005560:Formate Dehydrogenases; D005561:Formates / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D006864:Hydrogenase; D008190:Lyases / Q000235:genetics / Q000378:metabolism*; D009097:Multienzyme Complexes; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013696:Temperature; D015854:Up-Regulation
chemical_list: D005561:Formates; D009097:Multienzyme Complexes; D011994:Recombinant Proteins; C030544:formic acid; D006859:Hydrogen; D006864:Hydrogenase; D005560:Formate Dehydrogenases; C054017:formate hydrogenlyase; D008190:Lyases