title: Hydrogenotrophic sulfate reduction in a gas-lift bioreactor operated at 9 degrees C.
abstract: The viability of low temperature sulfate reduction with hydrogen as electron donor was studied with a bench-scale gas-lift bioreactor (GLB) operated at 9 degrees C. Prior to the GLB experiment, the temperature range of sulfate reduction of the inoculum was assayed. The results of the temperature gradient assay indicated that the inoculum was a psychrotolerant mesophilic enrichment culture that had an optimal temperature for sulfate reduction of 31 degrees C, and minimum and maximum temperatures of 7 degrees C and 41 degrees C, respectively. In the GLB experiment at 9 degrees C, a sulfate reduction rate of 500-600 mg L(-1) d(-1), corresponding to a specific activity of 173 mg SO(4)(2-) g VSS(-1) d(-1), was obtained. The electron flow from the consumed H(2)-gas to sulfate reduction varied between 27% and 52%, while the electron flow to acetate production decreased steadily from 15% to 5%. No methane was produced. Acetate was produced from CO(2) and H(2) by homoacetogenic bacteria. Acetate supported the growth of some heterotrophic sulfate-reducing bacteria. The sulfate reduction rate in the GLB was limited by the slow biomass growth rate at 9 degrees C and low biomass retention in the reactor. Nevertheless, this study demonstrated the potential sulfate reduction rate of psychrotolerant sulfate-reducing mesophiles at sub-optimal temperature.
authors.affiliation: Department of Chemistry and Bioengineering, Tampere University of Technology, P.O. Box 541, FIN-33101, Tampere, Finland. laura.nevatalo@tut.fi
authors.forename: Laura M
authors.initials: LM
authors.lastname: Nevatalo
authors.forename: Martijn F M
authors.initials: MF
authors.lastname: Bijmans
authors.forename: Piet N L
authors.initials: PN
authors.lastname: Lens
authors.forename: Anna H
authors.initials: AH
authors.lastname: Kaksonen
authors.forename: Jaakko A
authors.initials: JA
authors.lastname: Puhakka
mesh_terms: D018533:Biomass; D019149:Bioreactors / Q000382:microbiology*; D006859:Hydrogen / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D013431:Sulfates / Q000737:chemistry / Q000378:metabolism*; D016999:Sulfur-Reducing Bacteria / Q000737:chemistry / Q000378:metabolism*; D013696:Temperature; D014865:Waste Disposal, Fluid / Q000295:instrumentation / Q000379:methods*
chemical_list: D013431:Sulfates; D006859:Hydrogen