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Candry P, Flinkstrom Z, Henriikka Winkler MK. Wetlands harbor lactic acid-driven chain elongators. Microbiol Spectr 2024; 12:e0210523. [PMID: 38084977 PMCID: PMC10783096 DOI: 10.1128/spectrum.02105-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Accepted: 11/02/2023] [Indexed: 01/13/2024] Open
Abstract
IMPORTANCE Wetlands are globally significant carbon cycling hotspots that both sequester large amounts of CO2 as soil carbon as well as emit a third of all CH4 globally. Their outsized role in the global carbon cycle makes it critical to understand microbial processes contributing to carbon breakdown and storage in these ecosystems. Here, we confirm the presence of chain-elongating organisms in freshwater wetland soils. These organisms take small carbon compounds formed during the breakdown of biomass and turn them into larger compounds (six to eight carbon organic acids) that may potentially contribute to the formation of soil organic matter and long-term carbon storage. Moreover, we find that these chain-elongating organisms may be widely distributed in wetlands globally. Future work should identify these organisms' contribution to carbon cycling in wetlands and the potential role of the products they form in carbon sequestration in wetlands.
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Affiliation(s)
- Pieter Candry
- Civil and Environmental Engineering, University of Washington, Seattle, Washington, USA
| | - Zachary Flinkstrom
- Civil and Environmental Engineering, University of Washington, Seattle, Washington, USA
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Robles A, Sundar SV, Mohana Rangan S, Delgado AG. Butanol as a major product during ethanol and acetate chain elongation. Front Bioeng Biotechnol 2023; 11:1181983. [PMID: 37274171 PMCID: PMC10233103 DOI: 10.3389/fbioe.2023.1181983] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Accepted: 05/08/2023] [Indexed: 06/06/2023] Open
Abstract
Chain elongation is a relevant bioprocess in support of a circular economy as it can use a variety of organic feedstocks for production of valuable short and medium chain carboxylates, such as butyrate (C4), caproate (C6), and caprylate (C8). Alcohols, including the biofuel, butanol (C4), can also be generated in chain elongation but the bioreactor conditions that favor butanol production are mainly unknown. In this study we investigated production of butanol (and its precursor butyrate) during ethanol and acetate chain elongation. We used semi-batch bioreactors (0.16 L serum bottles) fed with a range of ethanol concentrations (100-800 mM C), a constant concentration of acetate (50 mM C), and an initial total gas pressure of ∼112 kPa. We showed that the butanol concentration was positively correlated with the ethanol concentration provided (up to 400 mM C ethanol) and to chain elongation activity, which produced H2 and further increased the total gas pressure. In bioreactors fed with 400 mM C ethanol and 50 mM C acetate, a concentration of 114.96 ± 9.26 mM C butanol (∼2.13 g L-1) was achieved after five semi-batch cycles at a total pressure of ∼170 kPa and H2 partial pressure of ∼67 kPa. Bioreactors with 400 mM C ethanol and 50 mM C acetate also yielded a butanol to butyrate molar ratio of 1:1. At the beginning of cycle 8, the total gas pressure was intentionally decreased to ∼112 kPa to test the dependency of butanol production on total pressure and H2 partial pressure. The reduction in total pressure decreased the molar ratio of butanol to butyrate to 1:2 and jolted H2 production out of an apparent stall. Clostridium kluyveri (previously shown to produce butyrate and butanol) and Alistipes (previously linked with butyrate production) were abundant amplicon sequence variants in the bioreactors during the experimental phases, suggesting the microbiome was resilient against changes in bioreactor conditions. The results from this study clearly demonstrate the potential of ethanol and acetate-based chain elongation to yield butanol as a major product. This study also supports the dependency of butanol production on limiting acetate and on high total gas and H2 partial pressures.
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Affiliation(s)
- Aide Robles
- Biodesign Swette Center for Environmental Biotechnology, Arizona State University, Tempe, AZ, United States
- School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ, United States
- Engineering Research Center for Bio-Mediated and Bio-Inspired Geotechnics, Arizona State University, Tempe, AZ, United States
| | - Skanda Vishnu Sundar
- Biodesign Swette Center for Environmental Biotechnology, Arizona State University, Tempe, AZ, United States
- School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ, United States
| | - Srivatsan Mohana Rangan
- Biodesign Swette Center for Environmental Biotechnology, Arizona State University, Tempe, AZ, United States
- School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ, United States
- Engineering Research Center for Bio-Mediated and Bio-Inspired Geotechnics, Arizona State University, Tempe, AZ, United States
| | - Anca G. Delgado
- Biodesign Swette Center for Environmental Biotechnology, Arizona State University, Tempe, AZ, United States
- School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ, United States
- Engineering Research Center for Bio-Mediated and Bio-Inspired Geotechnics, Arizona State University, Tempe, AZ, United States
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Mohana Rangan S, Rao S, Robles A, Mouti A, LaPat-Polasko L, Lowry GV, Krajmalnik-Brown R, Delgado AG. Decoupling Fe 0 Application and Bioaugmentation in Space and Time Enables Microbial Reductive Dechlorination of Trichloroethene to Ethene: Evidence from Soil Columns. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:4167-4179. [PMID: 36866930 PMCID: PMC10018760 DOI: 10.1021/acs.est.2c06433] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Revised: 12/28/2022] [Accepted: 02/14/2023] [Indexed: 06/06/2023]
Abstract
Fe0 is a powerful chemical reductant with applications for remediation of chlorinated solvents, including tetrachloroethene and trichloroethene. Its utilization efficiency at contaminated sites is limited because most of the electrons from Fe0 are channeled to the reduction of water to H2 rather than to the reduction of the contaminants. Coupling Fe0 with H2-utilizing organohalide-respiring bacteria (i.e., Dehalococcoides mccartyi) could enhance trichloroethene conversion to ethene while maximizing Fe0 utilization efficiency. Columns packed with aquifer materials have been used to assess the efficacy of a treatment combining in space and time Fe0 and aD. mccartyi-containing culture (bioaugmentation). To date, most column studies documented only partial conversion of the solvents to chlorinated byproducts, calling into question the feasibility of Fe0 to promote complete microbial reductive dechlorination. In this study, we decoupled the application of Fe0 in space and time from the addition of organic substrates andD. mccartyi-containing cultures. We used a column containing soil and Fe0 (at 15 g L-1 in porewater) and fed it with groundwater as a proxy for an upstream Fe0 injection zone dominated by abiotic reactions and biostimulated/bioaugmented soil columns (Bio-columns) as proxies for downstream microbiological zones. Results showed that Bio-columns receiving reduced groundwater from the Fe0-column supported microbial reductive dechlorination, yielding up to 98% trichloroethene conversion to ethene. The microbial community in the Bio-columns established with Fe0-reduced groundwater also sustained trichloroethene reduction to ethene (up to 100%) when challenged with aerobic groundwater. This study supports a conceptual model where decoupling the application of Fe0 and biostimulation/bioaugmentation in space and/or time could augment microbial trichloroethene reductive dechlorination, particularly under oxic conditions.
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Affiliation(s)
- Srivatsan Mohana Rangan
- School
of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, Arizona 85281, United States
- Biodesign
Swette Center for Environmental Biotechnology, Arizona State University, Tempe, Arizona 85287, United States
- Center
for Bio-Mediated and Bio-Inspired Geotechnics (CBBG), Arizona State University, Tempe, Arizona 85281, United States
- Biodesign
Center for Health Through Microbiomes, Arizona
State University, Tempe, Arizona 85287, United States
| | - Shefali Rao
- School
of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, Arizona 85281, United States
- Biodesign
Swette Center for Environmental Biotechnology, Arizona State University, Tempe, Arizona 85287, United States
- Center
for Bio-Mediated and Bio-Inspired Geotechnics (CBBG), Arizona State University, Tempe, Arizona 85281, United States
| | - Aide Robles
- School
of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, Arizona 85281, United States
- Biodesign
Swette Center for Environmental Biotechnology, Arizona State University, Tempe, Arizona 85287, United States
- Center
for Bio-Mediated and Bio-Inspired Geotechnics (CBBG), Arizona State University, Tempe, Arizona 85281, United States
| | - Aatikah Mouti
- Biodesign
Swette Center for Environmental Biotechnology, Arizona State University, Tempe, Arizona 85287, United States
| | | | - Gregory V. Lowry
- Center
for Environmental Implications of Nanotechnology (CEINT), Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
- Department
of Civil & Environmental Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Rosa Krajmalnik-Brown
- School
of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, Arizona 85281, United States
- Biodesign
Swette Center for Environmental Biotechnology, Arizona State University, Tempe, Arizona 85287, United States
- Center
for Bio-Mediated and Bio-Inspired Geotechnics (CBBG), Arizona State University, Tempe, Arizona 85281, United States
- Biodesign
Center for Health Through Microbiomes, Arizona
State University, Tempe, Arizona 85287, United States
| | - Anca G. Delgado
- School
of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, Arizona 85281, United States
- Biodesign
Swette Center for Environmental Biotechnology, Arizona State University, Tempe, Arizona 85287, United States
- Center
for Bio-Mediated and Bio-Inspired Geotechnics (CBBG), Arizona State University, Tempe, Arizona 85281, United States
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