title: Enhancement of photoheterotrophic biohydrogen production at elevated temperatures by the expression of a thermophilic clostridial hydrogenase.
abstract: The working temperature of a photobioreactor under sunlight can be elevated above the optimal growth temperature of a microorganism. To improve the biohydrogen productivity of photosynthetic bacteria at higher temperatures, a [FeFe]-hydrogenase gene from the thermophile Clostridium thermocellum was expressed in the mesophile Rhodopseudomonas palustris CGA009 (strain CGA-CThydA) using a log-phase expression promoter P(                            pckA                         ) to drive the expression of heterogeneous hydrogenase gene. In contrast, a mesophilic Clostridium acetobutylicum [FeFe]-hydrogenase gene was also constructed and expressed in R. palustris (strain CGA-CAhydA). Both transgenic strains were tested for cell growth, in vivo hydrogen production rate, and in vitro hydrogenase activity at elevated temperatures. Although both CGA-CThydA and CGA-CAhydA strains demonstrated enhanced growth over the vector control at temperatures above 38 °C, CGA-CThydA produced more hydrogen than the other strains. The in vitro hydrogenase activity assay, measured at 40 °C, confirmed that the activity of the CGA-CThydA hydrogenase was higher than the CGA-CAhydA hydrogenase. These results showed that the expression of a thermophilic [FeFe]-hydrogenase in R. palustris increased the growth rate and biohydrogen production at elevated temperatures. This transgenic strategy can be applied to a broad range of purple photosynthetic bacteria used to produce biohydrogen under sunlight.
authors.affiliation: Department of Life Sciences, National Chung Hsing University, 250 Kuo Kuang Road, Taichung, Taiwan, Republic of China.
authors.forename: Shou-Chen
authors.initials: SC
authors.lastname: Lo
authors.forename: Shau-Hua
authors.initials: SH
authors.lastname: Shih
authors.forename: Jui-Jen
authors.initials: JJ
authors.lastname: Chang
authors.forename: Chun-Ying
authors.initials: CY
authors.lastname: Wang
authors.forename: Chieh-Chen
authors.initials: CC
authors.lastname: Huang
mesh_terms: D001483:Base Sequence; D002849:Chromatography, Gas; D048013:Acetivibrio thermocellus / Q000201:enzymology*; D017931:DNA Primers; D004274:DNA, Recombinant; D006358:Hot Temperature; D006859:Hydrogen / Q000378:metabolism*; D006864:Hydrogenase / Q000378:metabolism*; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D012241:Rhodopseudomonas / Q000378:metabolism; D019076:Transgenes
chemical_list: D017931:DNA Primers; D004274:DNA, Recombinant; D000644:Quaternary Ammonium Compounds; D006859:Hydrogen; D006864:Hydrogenase