Middle-East Journal of Scientific Research 14 (9): 1242-1246, 2013 ISSN 1990-9233 © IDOSI Publications, 2013 DOI: 10.5829/idosi.mejsr.2013.14.9.0001 Corresponding Author: Dr. Ghasem Najafpour, Biotechnology Research Lab, Faculty of Chemical Engineering, Noshirvani University of Technology, Babol, Iran. Tel. /Fax: +98 111 321 0975. 1242 Effect of Ferric Citrate on Biohydrogen Production from Syngas Using Rhodopseudomonas palustris PT Fatemeh Pakpour, Maedeh Mohammadi and Ghasem D. Najafpour Biotechnology Research Lab, Faculty of Chemical Engineering, Noshirvani University of Technology, Babol, Iran Abstract: Biohydrogen production from synthesis gas (syngas) was investigated using a local bacterium isolated from anaerobic sludge of dairy wastewater. The isolated strain Rhodopseudomonas palustris PT was able to convert syngas to hydrogen through water shift gas (WGS) reaction. The aim of present study was to determine the optimum concentration of ferric citrate which avoids the cell growth inhibition and improves the activity of enzymes involved in BioWGS reaction. For this purpose, the influence of ferric citrate on cell growth, CO consumption and biohydrogen production was considered. Light and carbon monoxide were used for the first stage of bacterial growth; but throughout the hydrogen production stage, light was eliminated and carbon monoxide supplied the required energy for the cell through the exothermic WGS reaction. The optimum soluble concentration of ferric citrate was achieved at 27 mg/l with 33 mmol/l hydrogen production. It was found that high concentration of ferric citrate (90 mg/l) interfered with cell growth and hydrogen production. It was also found that ferric citrate may affect on enzymatic activity of hydrogenase and carbon monoxide dehydrogenase (CODH) in BioWGS reaction. Key words: Biohydrogen Syngas WGS reaction Ferric citrate INTRODUCTION CO + H O CO + H G= -20.1 kJ/mol (1) Hydrogen is an ideal synthetic fuel which leaves Hydrogenogenic bacteria like purple non-sulfur water vapor as by-product after combustion [1]. If photosynthetic bacteria such as Rhodopseudomonas hydrogen is going to be replaced with conventional palustris, Rhodosprillum rubrum, Rhodocyclus petroleum fuels in the near future, it has to be produced in gelatinosus and Rubrivivax gelatinosus CBS are large scale through renewable technologies. The trend commonly utilized for hydrogen production [4-6]. In towards environmental sustainability and utilization of biological WGS reaction, the required energy is renewable resources had significantly increased interests supplied by electron transferring from CO to H O in biological ways to produce hydrogen instead of through oxidation of CO to CO [7]. The hydrogenase conventional methods. The noticeable advantage of and CO dehydrogenase (CODH) are two significant biological hydrogen production is environmentally enzymes playing important roles in energy generation innocuous process which is performed under mild in the hydrogenogenic metabolism [8]. Hydrogenases operation condition [2]. catalyze the reduction of protons to hydrogen Generally, a mixture of gases are generated from molecules. variety of carbonaceous materials in traditional gasifiers, Hydrogen production from syngas requires called synthesis gas (syngas) including mainly CO, CO optimization of several parameters such as type and 2 and H [3]. Hydrogen production through BioWGS amount of carbon source, pH of growth medium, 2 reaction occurs through hydrogenogenic bacteria temperature and trace elements which affect the activity which convert CO and H O to CO and H according to of the two enzymes responsible for producing hydrogen 2 2 2 Equation (1): in the BioWSG reaction [9]. 2 2 2 2 2