title: Effects of pH and carbon sources on biohydrogen production by co-culture of Clostridium butyricum and Rhodobacter sphaeroides.
abstract: To improve the hydrogen yield from biological fermentation of organic wastewater, a co-culture system of dark- and photo-fermentation bacteria was investigated. In a pureculture system of the dark-fermentation bacterium Clostridium butyricum, a pH of 6.25 was found to be optimal, resulting in a hydrogen production rate of 18.7 ml-H₂/l/h. On the other hand, the photosynthetic bacterium Rhodobacter sphaeroides could produce the most hydrogen at 1.81 mol-H₂/mol-glucose at pH 7.0. The maximum specific growth rate of R. sphaeroides was determined to be 2.93 h⁻¹ when acetic acid was used as the carbon source, a result that was significantly higher than that obtained using either glucose or a mixture of volatile fatty acids (VFAs). Acetic acid best supported R. sphaeroides cell growth but not hydrogen production. In the co-culture system with glucose, hydrogen could be steadily produced without any lag phase. There were distinguishable inflection points in a plot of accumulated hydrogen over time, resulting from the dynamic production or consumption of VFAs by the interaction between the dark- and photofermentation bacteria. Lastly, the hydrogen production rate of a repeated fed-batch run was 15.9 ml-H₂/l/h, which was achievable in a sustainable manner.
authors.affiliation: Department of Environmental Engineering, Kyungpook National University, Daegu 702-701, Korea.
authors.forename: Jung-Yeol
authors.initials: JY
authors.lastname: Lee
authors.forename: Xue-Jiao
authors.initials: XJ
authors.lastname: Chen
authors.forename: Eun-Jung
authors.initials: EJ
authors.lastname: Lee
authors.forename: Kyung-Sok
authors.initials: KS
authors.lastname: Min
mesh_terms: D002244:Carbon / Q000378:metabolism*; D046972:Clostridium butyricum / Q000378:metabolism*; D018920:Coculture Techniques / Q000379:methods*; D005232:Fatty Acids, Volatile / Q000378:metabolism; D005285:Fermentation; D005947:Glucose / Q000378:metabolism; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D012242:Rhodobacter sphaeroides / Q000378:metabolism*
chemical_list: D005232:Fatty Acids, Volatile; D002244:Carbon; D006859:Hydrogen; D005947:Glucose