title: Anaerobic digestion of the microalga Spirulina at extreme alkaline conditions: biogas production, metagenome, and metatranscriptome.
abstract: A haloalkaline anaerobic microbial community obtained from soda lake sediments was used to inoculate anaerobic reactors for the production of methane rich biogas. The microalga Spirulina was successfully digested by the haloalkaline microbial consortium at alkaline conditions (pH 10, 2.0 M Na(+)). Continuous biogas production was observed and the obtained biogas was rich in methane, up to 96%. Alkaline medium acted as a CO2 scrubber which resulted in low amounts of CO2 and no traces of H2S in the produced biogas. A hydraulic retention time (HRT) of 15 days and 0.25 g Spirulina L(-1) day(-1) organic loading rate (OLR) were identified as the optimal operational parameters. Metagenomic and metatranscriptomic analysis showed that the hydrolysis of the supplied substrate was mainly carried out by Bacteroidetes of the "ML635J-40 aquatic group" while the hydrogenotrophic pathway was the main producer of methane in a methanogenic community dominated by Methanocalculus.
authors.affiliation: Institute for Genome Research and Systems Biology, Center for Biotechnology, University of Bielefeld Bielefeld, Germany.
authors.forename: Vímac
authors.initials: V
authors.lastname: Nolla-Ardèvol
authors.affiliation: Institute for Genome Research and Systems Biology, Center for Biotechnology, University of Bielefeld Bielefeld, Germany ; Department of Geoscience, University of Calgary Calgary, AB, Canada ; Microbial Fitness Group, Max Planck Institute for Marine Microbiology Bremen, Germany.
authors.forename: Marc
authors.initials: M
authors.lastname: Strous
authors.affiliation: Institute for Genome Research and Systems Biology, Center for Biotechnology, University of Bielefeld Bielefeld, Germany ; Microbial Fitness Group, Max Planck Institute for Marine Microbiology Bremen, Germany ; HGF-MPG Group for Deep Sea Ecology and Technology, Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research Bremerhaven, Germany.
authors.forename: Halina E
authors.initials: HE
authors.lastname: Tegetmeyer
keywords: Methanocalculus; Spirulina; alkaline lake; biogas; haloalkaline; methane rich; microalgae