Using Rhodopseudomonas palustris PT

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 be affected on enzymatic activity of hydrogenase and carbon monoxide dehydrogenase (CODH) in BioWGS reaction.