Article

Enhanced hydrogen production from formic acid by formate hydrogen lyase-overexpressing Escherichia coli strains.

Microbiology Research Group, Research Institute of Innovative Technology for the Earth, 9-2 Kizugawadai, Kizu-cho Soraku-gun, Kyoto 619-0292, Japan.
Applied and Environmental Microbiology (impact factor: 3.83). 12/2005; 71(11):6762-8. DOI:10.1128/AEM.71.11.6762-6768.2005 pp.6762-8
Source: PubMed

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.

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Keywords

2.8-fold increase
 
cell density
 
Continuous hydrogen production
 
conventional methods
 
Escherichia coli
 
FHL repressor
 
FHL)-overexpressing strain SR13
 
formate hydrogen lyase
 
free formic acid
 
genetic modification
 
Genetic recombination
 
hydrogen productivity
 
initial productivity
 
large-subunit formate dehydrogenase
 
novel method
 
practical application
 
reactor concentration
 
resultant strain SR13 2 orders
 
strain SR13
 
wild-type strain
 

Akihito Yoshida