title: Biohydrogen production from xylose by fresh and digested activated sludge at 37, 55 and 70 °C.
abstract: Two heat-treated inocula, fresh and digested activated sludge from the same municipal wastewater treatment plant, were compared for their H2production via dark fermentation at mesophilic (37 °C), thermophilic (55 °C) and hyperthermophilic (70 °C) conditions using xylose as the substrate. At both 37 and 55 °C, the fresh activated sludge yielded more H2than the digested sludge, whereas at 70 °C, neither of the inocula produced H2effectively. A maximum yield of 1.85 mol H2per mol of xylose consumed was obtained at 55 °C. H2production was linked to acetate and butyrate production, and there was a linear correlation (R2= 0.96) between the butyrate and H2yield for the fresh activated sludge inoculum at 55 °C. Approximately 2.4 mol H2per mol of butyrate produced were obtained against a theoretical maximum of 2.0, suggesting that H2was produced via the acetate pathway prior to switching to the butyrate pathway due to the increased H2partial pressure. Clostridia sp. were the prevalent species at both 37 and 55 °C, irrespectively of the inoculum type. Although the two inocula originated from the same plant, different thermophilic microorganisms were detected at 55 °C. Thermoanaerobacter sp., detected only in the fresh activated sludge cultures, may have contributed to the high H2yield obtained with such an inoculum.
authors.affiliation: Department of Chemistry and Bioengineering, Tampere University of Technology, Tampere, P.O. Box 541, FI-33101 Tampere, Finland. Electronic address: paolo.dessi@tut.fi.
authors.forename: Paolo
authors.initials: P
authors.lastname: Dessì
authors.affiliation: Department of Chemistry and Bioengineering, Tampere University of Technology, Tampere, P.O. Box 541, FI-33101 Tampere, Finland.
authors.forename: Aino-Maija
authors.initials: AM
authors.lastname: Lakaniemi
authors.affiliation: Department of Chemistry and Bioengineering, Tampere University of Technology, Tampere, P.O. Box 541, FI-33101 Tampere, Finland; UNESCO-IHE, Institute for Water Education, Westvest 7, 2611AX Delft, The Netherlands.
authors.forename: Piet N L
authors.initials: PNL
authors.lastname: Lens
mesh_terms: D019149:Bioreactors; D005285:Fermentation; D006859:Hydrogen / Q000378:metabolism; D012722:Sewage; D014994:Xylose
chemical_list: D012722:Sewage; D006859:Hydrogen; D014994:Xylose
keywords: Biohydrogen; Butyrate; Dark fermentation; Inocula; Temperature; Xylose