title: Microbial community response to addition of polylactate compounds to stimulate hexavalent chromium reduction in groundwater.
abstract: To evaluate the efficacy of bioimmobilization of Cr(VI) in groundwater at the Department of Energy Hanford site, we conducted a series of microcosm experiments using a range of commercial electron donors with varying degrees of lactate polymerization (polylactate). These experiments were conducted using Hanford Formation sediments (coarse sand and gravel) immersed in Hanford groundwater, which were amended with Cr(VI) and several types of lactate-based electron donors (Hydrogen Release Compound, HRC; primer-HRC, pHRC; extended release HRC) and the polylactate-cysteine form (Metal Remediation Compound, MRC). The results showed that polylactate compounds stimulated an increase in bacterial biomass and activity to a greater extent than sodium lactate when applied at equivalent carbon concentrations. At the same time, concentrations of headspace hydrogen and methane increased and correlated with changes in the microbial community structure. Enrichment of Pseudomonas spp. occurred with all lactate additions, and enrichment of sulfate-reducing Desulfosporosinus spp. occurred with almost complete sulfate reduction. The results of these experiments demonstrate that amendment with the pHRC and MRC forms result in effective removal of Cr(VI) from solution most likely by both direct (enzymatic) and indirect (microbially generated reductant) mechanisms.
authors.affiliation: Ecology Department, Earth Sciences Division, Lawrence Berkeley National Laboratory, CA 94720, United States. elbrodie@lbl.gov
authors.forename: Eoin L
authors.initials: EL
authors.lastname: Brodie
authors.forename: Dominique C
authors.initials: DC
authors.lastname: Joyner
authors.forename: Boris
authors.initials: B
authors.lastname: Faybishenko
authors.forename: Mark E
authors.initials: ME
authors.lastname: Conrad
authors.forename: Carlos
authors.initials: C
authors.lastname: Rios-Velazquez
authors.forename: Josue
authors.initials: J
authors.lastname: Malave
authors.forename: Ramon
authors.initials: R
authors.lastname: Martinez
authors.forename: Benjamin
authors.initials: B
authors.lastname: Mork
authors.forename: Anna
authors.initials: A
authors.lastname: Willett
authors.forename: Steven
authors.initials: S
authors.lastname: Koenigsberg
authors.forename: Donald J
authors.initials: DJ
authors.lastname: Herman
authors.forename: Mary K
authors.initials: MK
authors.lastname: Firestone
authors.forename: Terry C
authors.initials: TC
authors.lastname: Hazen
mesh_terms: D001673:Biodegradation, Environmental; D018533:Biomass; D002857:Chromium / Q000737:chemistry / Q000378:metabolism*; D019015:Geologic Sediments / Q000382:microbiology; D060587:Groundwater / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000378:metabolism* / Q000494:pharmacology; D010459:Peptococcaceae / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D011091:Polyesters; D011108:Polymers / Q000378:metabolism* / Q000494:pharmacology; D011549:Pseudomonas / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D012336:RNA, Ribosomal, 16S / Q000378:metabolism
chemical_list: D011091:Polyesters; D011108:Polymers; D012336:RNA, Ribosomal, 16S; D002857:Chromium; C074702:chromium hexavalent ion; D019344:Lactic Acid; C033616:poly(lactide)