Oxygen insentive hydrogen production in a recombinant hyperthermophilic archaeon, Thermococcus onnurineus NA1 overexpressing frh hydrogenase

Abstract

In order to understand the in vivo role of soluble hydrogenase encoded by a gene cluster comprised of frhAGB in hyperthermophilic archaeon T. onnurineus NA1, we made a recombinant by overexpressing the frh gene cluster and tried to understand the changes in the mutant by employing microarray-based whole transcriptome analysis. As a result, it was revealed that overexpression of frhAGB genes caused up-regulation of several genes involved in stress response genes such as thermosome beta subunit, universal stress protein, peroxiredoxin and alkyl hydroperoxide reductase subunit C. Probably related with the up-regulation of stress response genes, the mutant exhibited significantly enhanced growth and resistance to O2 when cultured on formate-containing medium as an energy source. Furthermore, exposure of 50 % air in the headspace of sealed bottle did not ameliorate growth of the mutant. Even further, we tested growth and H2 production of the mutant in a bioreactor culture without deoxygenization steps such as autoclave and nitrogen purging system and found that lag phase prolonged but final growth yield and H2 production were not affected. Consequently, we could demonstrate biohydrogen production without oxygen removal of obligate anaerobic hyperthermophilic archaeon by overexpression of frhAGB hydrogenasend the changes in the mutant by employing microarray-based whole transcriptome analysis. As a result, it was revealed that overexpression of frhAGB genes caused up-regulation of several genes involved in stress response genes such as thermosome beta subunit, universal stress protein, peroxiredoxin and alkyl hydroperoxide reductase subunit C. Probably related with the up-regulation of stress response genes, the mutant exhibited significantly enhanced growth and resistance to O2 when cultured on formate-containing medium as an energy source. Furthermore, exposure of 50 % air in the headspace of sealed bottle did not ameliorate growth of the mutant. Even further, we tested growth and H2 production of the mutant in a bioreactor culture without deoxygenization steps such as autoclave and nitrogen purging system and found that lag phase prolonged but final growth yield and H2 production were not affected. Consequently, we could demonstrate biohydrogen production without oxygen removal of obligate anaerobic hyperthermophilic archaeon by overexpression of frhAGB hydrogenase