title: Hydrogen production by hup(-) mutant and wild-type strains of Rhodobacter capsulatus from dark fermentation effluent of sugar beet thick juice in batch and continuous photobioreactors.
abstract: Photofermentative production of hydrogen is a promising and sustainable process; however, it should be coupled to dark fermentation to become cost effective. In order to integrate dark fermentation and photofermentation, the suitability of dark fermenter effluents for the photofermentative hydrogen production must be demonstrated. In this study, thermophilic dark fermenter effluent (DFE) of sugar beet thick juice was used as a substrate in photofermentation process to compare wild-type and uptake hydrogenase-deficient (hup (-)) mutant strains of Rhodobacter capsulatus by means of hydrogen production and biomass growth. The tests were conducted in small-scale (50 mL) batch and large-scale (4 L) continuous photobioreactors in indoor conditions under continuous illumination. In small scale batch conditions, maximum cell concentrations were 0.92 gdcw/L c and 1.50 gdcw/L c, hydrogen yields were 34 % and 31 %, hydrogen productivities were 0.49 mmol/(L c·h) and 0.26 mmol/(Lc·h), for hup (-) and wild-type cells, respectively. In large-scale continuous conditions, maximum cell concentrations were 1.44 gdcw/L c and 1.87 gdcw/L c, hydrogen yields were 48 and 46 %, and hydrogen productivities were 1.01 mmol/(L c·h) and 1.05 mmol/(L c·h), for hup (-) and wild-type cells, respectively. Our results showed that Rhodobacter capsulatus hup (-) cells reached to a lower maximum cell concentration but their hydrogen yield and productivity were in the same range or superior compared to the wild-type cells in both batch and continuous operating modes. The maximum biomass concentration, yield and productivity of hydrogen were higher in continuous mode compared to the batch mode with both bacterial strains.
authors.affiliation: Department of Chemical Engineering, Kocaeli University, Kocaeli, Turkey. basar.uyar@kocaeli.edu.tr.
authors.forename: Basar
authors.initials: B
authors.lastname: Uyar
authors.affiliation: Department of Biological Sciences, Middle East Technical University, Ankara, Turkey. muazzez@metu.edu.tr.
authors.forename: Muazzez
authors.initials: M
authors.lastname: Gürgan
authors.affiliation: Micro-Electro-Mechanical Systems, Middle East Technical University, Ankara, Turkey. bebru@metu.edu.tr.
authors.forename: Ebru
authors.initials: E
authors.lastname: Özgür
authors.affiliation: Department of Biological Sciences, Middle East Technical University, Ankara, Turkey. ufukg@metu.edu.tr.
authors.forename: Ufuk
authors.initials: U
authors.lastname: Gündüz
authors.affiliation: Department of Biological Sciences, Middle East Technical University, Ankara, Turkey. meraly@metu.edu.tr.
authors.forename: Meral
authors.initials: M
authors.lastname: Yücel
authors.affiliation: Department of Chemical Engineering, Middle East Technical University, Ankara, Turkey. ieroglu@metu.edu.tr.
authors.forename: Inci
authors.initials: I
authors.lastname: Eroglu
mesh_terms: D027461:Beta vulgaris / Q000382:microbiology*; D056804:Biofuels / Q000382:microbiology*; D009154:Mutation; D058433:Photobioreactors / Q000382:microbiology*; D010936:Plant Extracts / Q000378:metabolism; D016354:Rhodobacter capsulatus / Q000145:classification / Q000235:genetics* / Q000378:metabolism*; D013045:Species Specificity; D014871:Water Microbiology; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D056804:Biofuels; D010936:Plant Extracts; D014874:Water Pollutants, Chemical
keywords: Biohydrogen; Photofermentation; Rhodobacter capsulatus; Sugar beet thick juice