title: Hydrogen-fed biofilm reactors reducing selenate and sulfate: Community structure and capture of elemental selenium within the biofilm.
abstract: Remediation of selenate (SeO4 (2-) ) contamination through microbial reduction is often challenging due to the presence of sulfate (SO4 (2-) ), which can lead to competition for the electron donor and the co-production of toxic H2 S. Microbial reduction of SeO4 (2-) in the presence of SO4 (2-) was studied in two hydrogen-based membrane biofilm reactors (MBfRs). One MBfR was initiated with SO4 (2-) -reducing conditions and gradually shifted to SeO4 (2-) reduction. The second MBfR was developed with a SeO4 (2-) -reducing biofilm, followed by SO4 (2-) introduction. Biofilms within both MBfRs achieved greater than 90% SeO4 (2-) reduction, even though the SeO4 (2-) concentration ranged from 1,000-11,000 μg/L, more than 20-200 times the maximum contaminant level for drinking water (50 μg/L). Biofilm microbial community composition, assessed by 16S rRNA gene-based amplicon pyrosequencing, was distinct between the two MBfRs and was framed by alterations in SeO4 (2-) loading. Specifically, high SeO4 (2-) loading resulted in communities mainly composed of denitrifying bacteria (e.g., Denitratisoma and Dechloromonas). In contrast, low loading led to mostly sulfate-reducing bacteria (i.e., Desulfovibrio) and sulfur-oxidizing bacteria (i.e., Sulfuricurvum and Sulfurovum). SeO4 (2-) was reduced to elemental selenium (Se°), which was visualized within the biofilm as crystalloid aggregates, with its fate corresponding to that of biofilm solids. In conclusion, microbial biofilm communities initiated under either SeO4 (2-) or SO4 (2-) -reducing conditions attained high SeO4 (2-) removal rates even though their microbial community composition was quite distinct. Biotechnol. Bioeng. 2016;113: 1736-1744. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Swette Center for Environmental Biotechnology, Biodesign Institute, Arizona State University, 1001 South McAllister Ave. Tempe, Arizona, 85287-5701.
authors.forename: Aura
authors.initials: A
authors.lastname: Ontiveros-Valencia
authors.affiliation: College of Letters and Sciences, Arizona State University, Mesa, Arizona.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Penton
authors.affiliation: Swette Center for Environmental Biotechnology, Biodesign Institute, Arizona State University, 1001 South McAllister Ave. Tempe, Arizona, 85287-5701.|School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, Arizona.
authors.forename: Rosa
authors.initials: R
authors.lastname: Krajmalnik-Brown
authors.affiliation: Swette Center for Environmental Biotechnology, Biodesign Institute, Arizona State University, 1001 South McAllister Ave. Tempe, Arizona, 85287-5701. rittmann@asu.edu.|School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, Arizona. rittmann@asu.edu.
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Rittmann
mesh_terms: D001419:Bacteria / Q000235:genetics; D018441:Biofilms; D019149:Bioreactors / Q000382:microbiology*; D006859:Hydrogen / Q000378:metabolism*; D064586:Selenic Acid / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D012643:Selenium / Q000032:analysis / Q000302:isolation & purification / Q000378:metabolism*; D013431:Sulfates / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*
chemical_list: D013431:Sulfates; D006859:Hydrogen; D012643:Selenium; D064586:Selenic Acid
keywords: TEM-EDX; biofilm; pyrosequencing; selenate; sulfate; sulfur-oxidizers