title: Biohydrogen production from wheat straw hydrolysate by dark fermentation using extreme thermophilic mixed culture.
abstract: Hydrolysate was tested as substrate for hydrogen production by extreme thermophilic mixed culture (70 degrees C) in both batch and continuously fed reactors. Hydrogen was produced at hydrolysate concentrations up to 25% (v/v), while no hydrogen was produced at hydrolysate concentration of 30% (v/v), indicating that hydrolysate at high concentrations was inhibiting the hydrogen fermentation process. In addition, the lag phase for hydrogen production was strongly influenced by the hydrolysate concentration, and was prolonged from approximately 11 h at the hydrolysate concentrations below 20% (v/v) to 38 h at the hydrolysate concentration of 25% (v/v). The maximum hydrogen yield as determined in batch assays was 318.4 +/- 5.2 mL-H(2)/g-sugars (14.2 +/- 0.2 mmol-H(2)/g-sugars) at the hydrolysate concentration of 5% (v/v). Continuously fed, and the continuously stirred tank reactor (CSTR), operating at 3 day hydraulic retention time (HRT) and fed with 20% (v/v) hydrolysate could successfully produce hydrogen. The hydrogen yield and production rate were 178.0 +/- 10.1 mL-H(2)/g-sugars (7.9 +/- 0.4 mmol H(2)/g-sugars) and 184.0 +/- 10.7 mL-H(2)/day L(reactor) (8.2 +/- 0.5 mmol-H(2)/day L(reactor)), respectively, corresponding to 12% of the chemical oxygen demand (COD) from sugars. Additionally, it was found that toxic compounds, furfural and hydroxymethylfurfural (HMF), contained in the hydrolysate were effectively degraded in the CSTR, and their concentrations were reduced from 50 and 28 mg/L, respectively, to undetectable concentrations in the effluent. Phylogenetic analysis of the mixed culture revealed that members involved hydrogen producers in both batch and CSTR reactors were phylogenetically related to the Caldanaerobacter subteraneus, Thermoanaerobacter subteraneus, and Thermoanaerobacterium thermosaccharolyticum.
authors.affiliation: Department of Environmental Engineering, Technical University of Denmark, DK-2800 Lyngby, Denmark.
authors.forename: Prawit
authors.initials: P
authors.lastname: Kongjan
authors.forename: Sompong
authors.initials: S
authors.lastname: O-Thong
authors.forename: Meher
authors.initials: M
authors.lastname: Kotay
authors.forename: Booki
authors.initials: B
authors.lastname: Min
authors.forename: Irini
authors.initials: I
authors.lastname: Angelidaki
mesh_terms: D019149:Bioreactors / Q000382:microbiology*; D004269:DNA, Bacterial / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D005285:Fermentation; D006094:Gram-Positive Bacteria / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D006358:Hot Temperature; D006859:Hydrogen / Q000378:metabolism*; D056186:Metagenomics; D009691:Nucleic Acid Denaturation; D018547:Plant Stems / Q000378:metabolism*; D014908:Triticum / Q000378:metabolism*
chemical_list: D004269:DNA, Bacterial; D006859:Hydrogen