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Pérez V, Lebrero R, Muñoz R, Pérez R. The fundamental role of pH in CH4 bioconversion into polyhydroxybutyrate in mixed methanotrophic cultures. CHEMOSPHERE 2024; 355:141832. [PMID: 38570044 DOI: 10.1016/j.chemosphere.2024.141832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Revised: 03/13/2024] [Accepted: 03/26/2024] [Indexed: 04/05/2024]
Abstract
Climate change and plastic pollution are likely the most relevant challenges for the environment in the 21st century. Developing cost-effective technologies for the bioconversion of methane (CH4) into polyhydroxyalkanoates (PHAs) could simultaneously mitigate CH4 emissions and boost the commercialization of biodegradable polymers. Despite the fact that the role of temperature, nitrogen deprivation, CH4:O2 ratio or micronutrients availability on the PHA accumulation capacity of methanotrophs has been carefully explored, there is still a need for optimization of the CH4-to-PHA bioconversion process prior to becoming a feasible platform in future biorefineries. In this study, the influence of different cultivation broth pH values (5.5, 7, 8.5 and 10) on bacterial biomass growth, CH4 bioconversion rate, PHA accumulation capacity and bacterial community structure was investigated in a stirred tank bioreactor under nitrogen deprivation conditions. Higher CH4 elimination rates were obtained at increasing pH, with a maximum value of 50.4 ± 2.7 g CH4·m-3·h-1 observed at pH 8.5. This was likely mediated by an increased ionic strength in the mineral medium, which enhanced the gas-liquid mass transfer. Interestingly, higher PHB accumulations were observed at decreasing pH, with the highest PHB contents recorded at a pH 5.5 (43.7 ± 3.4 %w·w-1). The strong selective pressure of low pH towards the growth of Type II methanotrophic bacteria could explain this finding. The genus Methylocystis increased its abundance from 34 % up to 85 and 90 % at pH 5.5 and 7, respectively. On the contrary, Methylocystis was less abundant in the community enriched at pH 8.5 (14 %). The accumulation of intracellular PHB as energy and carbon storage material allowed the maintenance of high CH4 biodegradation rates during 48 h after complete nitrogen deprivation. The results here obtained demonstrated for the first time a crucial and multifactorial role of pH on the bioconversion performance of CH4 into PHA.
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Affiliation(s)
- V Pérez
- Institute of Sustainable Processes, Valladolid University, Dr. Mergelina s/n, Spain; Department of Chemical Engineering and Environmental Technology, Valladolid University, Prado de la Magdalena 5, Valladolid, Spain
| | - R Lebrero
- Institute of Sustainable Processes, Valladolid University, Dr. Mergelina s/n, Spain; Department of Chemical Engineering and Environmental Technology, Valladolid University, Prado de la Magdalena 5, Valladolid, Spain
| | - R Muñoz
- Institute of Sustainable Processes, Valladolid University, Dr. Mergelina s/n, Spain; Department of Chemical Engineering and Environmental Technology, Valladolid University, Prado de la Magdalena 5, Valladolid, Spain
| | - R Pérez
- Institute of Sustainable Processes, Valladolid University, Dr. Mergelina s/n, Spain; Department of Chemical Engineering and Environmental Technology, Valladolid University, Prado de la Magdalena 5, Valladolid, Spain.
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Han H, Kim DD, Song MJ, Yun T, Yoon H, Lee HW, Kim YM, Laureni M, Yoon S. Biotrickling Filtration for the Reduction of N 2O Emitted during Wastewater Treatment: Results from a Long-Term In Situ Pilot-Scale Testing. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:3883-3892. [PMID: 36809918 DOI: 10.1021/acs.est.2c08818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Wastewater treatment plants (WWTPs) are a major source of N2O, a potent greenhouse gas with 300 times higher global warming potential than CO2. Several approaches have been proposed for mitigation of N2O emissions from WWTPs and have shown promising yet only site-specific results. Here, self-sustaining biotrickling filtration, an end-of-the-pipe treatment technology, was tested in situ at a full-scale WWTP under realistic operational conditions. Temporally varying untreated wastewater was used as trickling medium, and no temperature control was applied. The off-gas from the covered WWTP aerated section was conveyed through the pilot-scale reactor, and an average removal efficiency of 57.9 ± 29.1% was achieved during 165 days of operation despite the generally low and largely fluctuating influent N2O concentrations (ranging between 4.8 and 96.4 ppmv). For the following 60-day period, the continuously operated reactor system removed 43.0 ± 21.2% of the periodically augmented N2O, exhibiting elimination capacities as high as 5.25 g N2O m-3·h-1. Additionally, the bench-scale experiments performed abreast corroborated the resilience of the system to short-term N2O starvations. Our results corroborate the feasibility of biotrickling filtration for mitigating N2O emitted from WWTPs and demonstrate its robustness toward suboptimal field operating conditions and N2O starvation, as also supported by analyses of the microbial compositions and nosZ gene profiles.
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Affiliation(s)
- Heejoo Han
- Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
| | - Daehyun D Kim
- Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
| | - Min Joon Song
- Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
| | - Taeho Yun
- Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
| | - Hyun Yoon
- Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
- School of Civil & Environmental Engineering, Cornell University, Ithaca, New York 14853, United States
| | | | - Young Mo Kim
- Department of Civil and Environmental Engineering, Hanyang University, Seoul 04763, South Korea
| | - Michele Laureni
- Department of Geoscience and Engineering, Delft University of Technology, 2628 CN Delft, The Netherlands
| | - Sukhwan Yoon
- Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
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Lu X, Wang Z, Duan H, Wu Z, Hu S, Ye L, Yuan Z, Zheng M. Significant production of nitric oxide by aerobic nitrite reduction at acidic pH. WATER RESEARCH 2023; 230:119542. [PMID: 36603308 DOI: 10.1016/j.watres.2022.119542] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 12/20/2022] [Accepted: 12/27/2022] [Indexed: 06/17/2023]
Abstract
The acidic (i.e., pH ∼5) activated sludge process is attracting attention because it enables stable nitrite accumulation and enhances sludge reduction and stabilization, compared to the conventional process at neutral pH. Here, this study examined the production and potential pathways of nitric oxide (NO) and nitrous oxide (N2O) during acidic sludge digestion. With continuous operation of a laboratory-scale aerobic digester at high dissolved oxygen concentration (DO>4 mg O2 L-1) and low pH (4.7±0.6), a significant amount of total nitrogen (TN) loss (i.e., 18.6±1.5% of TN in feed sludge) was detected. Notably, ∼40% of the removed TN was emitted as NO, with ∼8% as N2O. A series of batch assays were then designed to explain the observed TN loss under aerobic conditions. All assays were conducted with a low concentration of volatile solids (VS), i.e., VS<4.5 g L-1. This VS concentration is commensurate with the values commonly found in the aeration tanks of full-scale wastewater treatment systems, and thus no significant nitrogen loss should be expected when DO is controlled above 4 mg O2 L-1. However, nitrite disappeared at a significant rate (with the chemical decomposition of nitrite excluded), leading to NO production in the batch assays at pH 5. The nitrite reduction could be associated with endogenous microbial activities, e.g., nitrite detoxification. The significant NO production illustrates the importance of aerobic nitrite reduction during acidic aerobic sludge digestion, suggesting this process cannot be neglected in developing acidic activated sludge technology.
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Affiliation(s)
- Xi Lu
- Australian Centre for Water and Environmental Biotechnology, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Zhiyao Wang
- Australian Centre for Water and Environmental Biotechnology, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Haoran Duan
- Australian Centre for Water and Environmental Biotechnology, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Ziping Wu
- School of Chemical Engineering, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Shihu Hu
- Australian Centre for Water and Environmental Biotechnology, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Liu Ye
- School of Chemical Engineering, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Zhiguo Yuan
- Australian Centre for Water and Environmental Biotechnology, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Min Zheng
- Australian Centre for Water and Environmental Biotechnology, The University of Queensland, St Lucia, QLD 4072, Australia.
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Duan H, Zhao Y, Koch K, Wells GF, Zheng M, Yuan Z, Ye L. Insights into Nitrous Oxide Mitigation Strategies in Wastewater Treatment and Challenges for Wider Implementation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:7208-7224. [PMID: 33975433 DOI: 10.1021/acs.est.1c00840] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Nitrous oxide (N2O) emissions account for the majority of the carbon footprint of wastewater treatment plants (WWTPs). Many N2O mitigation strategies have since been developed while a holistic view is still missing. This article reviews the state-of-the-art of N2O mitigation studies in wastewater treatment. Through analyzing existing studies, this article presents the essential knowledge to guide N2O mitigations, and the logics behind mitigation strategies. In practice, mitigations are mainly carried out by aeration control, feed scheme optimization, and process optimization. Despite increasingly more studies, real implementation remains rare, which is a combined result of unclear climate change policies/incentives, as well as technical challenges. Five critical technical challenges, as well as opportunities, of N2O mitigations were identified. It is proposed that (i) quantification methods for overall N2O emissions and pathway contributions need improvement; (ii) a reliable while straightforward mathematical model is required to quantify benefits and compare mitigation strategies; (iii) tailored risk assessment needs to be conducted for WWTPs, in which more long-term full-scale trials of N2O mitigation are urgently needed to enable robust assessments of the resulting operational costs and impact on nutrient removal performance; (iv) current mitigation strategies focus on centralized WWTPs, more investigations are warranted for decentralised systems, especially decentralized activated sludge WWTPs; and (v) N2O may be mitigated by adopting novel strategies promoting N2O reduction denitrification or microorganisms that emit less N2O. Overall, we conclude N2O mitigation research is reaching a maturity while challenges still exist for a wider implementation, especially in relation to the reliability of N2O mitigation strategies and potential risks to nutrient removal performances of WWTPs.
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Affiliation(s)
- Haoran Duan
- School of Chemical Engineering, the University of Queensland, St. Lucia, Queensland 4072, Australia
- Advanced Water Management Centre (AWMC), the University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Yingfen Zhao
- School of Chemical Engineering, the University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Konrad Koch
- Chair of Urban Water Systems Engineering, Technical University of Munich, Am Coulombwall 3, 85748 Garching, Germany
| | - George F Wells
- Department of Civil and Environmental Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Min Zheng
- Advanced Water Management Centre (AWMC), the University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Zhiguo Yuan
- Advanced Water Management Centre (AWMC), the University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Liu Ye
- School of Chemical Engineering, the University of Queensland, St. Lucia, Queensland 4072, Australia
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Pérez R, Casal J, Muñoz R, Lebrero R. Polyhydroxyalkanoates production from methane emissions in Sphagnum mosses: Assessing the effect of temperature and phosphorus limitation. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 688:684-690. [PMID: 31254834 DOI: 10.1016/j.scitotenv.2019.06.296] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 06/10/2019] [Accepted: 06/19/2019] [Indexed: 06/09/2023]
Abstract
The isolation of highly efficient methanotrophic communities is crucial for the optimization of methane bioconversion into products with a high market value such as polyhydroxyalkanoates (PHA). The research here presented aimed at enriching a methanotrophic consortium from two different inocula (Sphagnum peat moss (Sp) and Sphagnum and activated sludge (M)) able to accumulate PHA while efficiently oxidizing CH4. Moreover, the effect of the temperature and phosphorus limitation on the biodegradation rate of CH4 and the PHA accumulation potential was investigated. Higher CH4 degradation rates were obtained under P availability at increasing temperature (25, 30 and 37 °C). The biomass enriched from the mixed inoculum always exhibited a superior biodegradation performance regardless of the temperature (a maximum value of 84.3 ± 8.4 mg CH4 h-1 g biomass-1 was recorded at 37 °C). The results of the PHB production showed that phosphorus limitation is required to promote PHB accumulation, the highest PHB content being observed with the Sphagnum inoculum at 25 °C (13.6 ± 5.6%). The differential specialization of the microbial communities depending on the enrichment temperature supported the key role of this parameter on the results obtained. In all cases after the completion of the enrichment process and of the P limitation tests, Methylocystis, a type II methanotroph known for its ability to accumulate PHA, was the genus that became dominant (reaching percentages from 16 to 46% depending on the enrichment temperature). Thus, the results here obtained demonstrated for the first time the relevance of the temperature used for the enrichment of the methanotrophic bacteria to boost PHA production yields under P limiting condition, highlighting the importance of optimizing culture conditions to improve the cost-efficiency of bioprocesses based on using methane as the primary feedstock for the PHA industrial market.
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Affiliation(s)
- Rebeca Pérez
- Department of Chemical Engineering and Environmental Technology, School of Industrial Engineering, Valladolid University, Prado de la Magdalena, 5, Valladolid, Spain; Institute of Sustainable Processes, Valladolid University, Spain.
| | - Jesús Casal
- Department of Chemical Engineering and Environmental Technology, School of Industrial Engineering, Valladolid University, Prado de la Magdalena, 5, Valladolid, Spain
| | - Raúl Muñoz
- Department of Chemical Engineering and Environmental Technology, School of Industrial Engineering, Valladolid University, Prado de la Magdalena, 5, Valladolid, Spain; Institute of Sustainable Processes, Valladolid University, Spain
| | - Raquel Lebrero
- Department of Chemical Engineering and Environmental Technology, School of Industrial Engineering, Valladolid University, Prado de la Magdalena, 5, Valladolid, Spain; Institute of Sustainable Processes, Valladolid University, Spain
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Thakur IS, Medhi K. Nitrification and denitrification processes for mitigation of nitrous oxide from waste water treatment plants for biovalorization: Challenges and opportunities. BIORESOURCE TECHNOLOGY 2019; 282:502-513. [PMID: 30898409 DOI: 10.1016/j.biortech.2019.03.069] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 03/12/2019] [Accepted: 03/13/2019] [Indexed: 06/09/2023]
Abstract
Nitrous oxide (N2O) is a potent greenhouse gas. Even though its emissions is much lesser than CO2 but its global warming potential (GWP) is 298 times more than CO2. N2O emissions from wastewater treatment plants was caused due to incomplete nitrification or incomplete denitrification catalyzed by ammonia-oxidizing bacteria and heterotrophic denitrifiers. Low dissolved oxygen, high nitrite accumulation, change in optimal pH or temperature, fluctuation in C/N ratio, short solid retention time and non-availability of Cu ions were responsible for higher N2O leakage. Regulation of enzyme metabolic pathways involved in N2O production and reduction has also been reviewed. Sequential bioreactors, bioscrubbers, membrane biofilters usage have helped microbial nitrification-denitrification processes in succumbing N2O production in wastewater treatment plants. Reduction of N2O negativity has been studied through its valorization for the formation of value added products such as biopolymers has led to biorefinery approaches as an upcoming mitigation strategy.
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Affiliation(s)
- Indu Shekhar Thakur
- School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110067, India.
| | - Kristina Medhi
- School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110067, India
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Palomo-Briones R, Esquivel-González S, Aizpuru A, Gómez-Hernández N, Casas-Flores S, Barba de la Rosa AP, Arriaga S. Microbial contamination in methanol biofilters inoculated with a pure strain of Pichia pastoris: A potential limitation for waste revalorization. Biotechnol Prog 2018; 35:e2715. [PMID: 30294912 DOI: 10.1002/btpr.2715] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Revised: 08/27/2018] [Indexed: 11/05/2022]
Abstract
Novel biotechnologies to valorize waste emissions are based on the use of specialized microbial groups that produce different compounds of industrial interest. On this scenario, the retention of such specific microorganisms in the system is of critical interest; however, the potential limitations of working with simplified cultures in a competitive open environment are neither fully explored nor well understood. In this work, a series of biofilters treating methanol vapors coupled with heterologous endochitinase production were used to evaluate the performance of a specialized microbial population during a typical open-to-environment operation. The biofilters were inoculated with a transformed strain of Pichia pastoris and were operated identically for about 90 days. The results showed that the biofiltration performance became diverse with time in terms of the elimination capacity (EC) shifting from a variation coefficient of 1.5% (EC = 274 ± 24, 279 ± 5, and 281.9 ± 25 g/[m3 h]) at the beginning of the operation to 33% (EC = 297 ± 9, 338 ± 7, and 341 ± 2 g/[m3 h]) at the end of operation. Epifluorescence analysis and cloning-sequencing suggested that P. pastoris remained as the dominant microorganism of methanol degradation, whereas diverse airborne bacteria, including Ochrobactrum spp. and Klebsiella oxytoca, played a secondary role possibly associated with the consumption of intermediates. Overall, this study found that low diversity systems operated under non-sterile conditions could be susceptible to contamination with external microorganisms causing a diversifying behavior at the performance and microbial community levels. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2715, 2019.
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Affiliation(s)
- Rodolfo Palomo-Briones
- Div. de Ciencias Ambientales, Instituto Potosino de Investigación Científica y Tecnológica (IPICYT), San Luis Potosí, San Luis Potosí, México
| | - Saúl Esquivel-González
- Div. de Ciencias Ambientales, Instituto Potosino de Investigación Científica y Tecnológica (IPICYT), San Luis Potosí, San Luis Potosí, México
| | - Aitor Aizpuru
- Universidad del Mar, Campus Purto Ángel, San Pedro Pochutla, México
| | - Nicolás Gómez-Hernández
- Div. de Biología Molecular, Instituto Potosino de Investigación Científica y Tecnológica (IPICYT), San Luis Potosí, San Luis Potosí, México
| | - Sergio Casas-Flores
- Div. de Biología Molecular, Instituto Potosino de Investigación Científica y Tecnológica (IPICYT), San Luis Potosí, San Luis Potosí, México
| | - Ana Paulina Barba de la Rosa
- Div. de Biología Molecular, Instituto Potosino de Investigación Científica y Tecnológica (IPICYT), San Luis Potosí, San Luis Potosí, México
| | - Sonia Arriaga
- Div. de Ciencias Ambientales, Instituto Potosino de Investigación Científica y Tecnológica (IPICYT), San Luis Potosí, San Luis Potosí, México
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A state-of-the-art review on nitrous oxide control from waste treatment and industrial sources. Biotechnol Adv 2018; 36:1025-1037. [DOI: 10.1016/j.biotechadv.2018.03.004] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 03/02/2018] [Accepted: 03/10/2018] [Indexed: 02/01/2023]
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Lai CY, Lv PL, Dong QY, Yeo SL, Rittmann BE, Zhao HP. Bromate and Nitrate Bioreduction Coupled with Poly-β-hydroxybutyrate Production in a Methane-Based Membrane Biofilm Reactor. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:7024-7031. [PMID: 29785845 DOI: 10.1021/acs.est.8b00152] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
This work demonstrates bromate (BrO3-) reduction in a methane (CH4)-based membrane biofilm reactor (MBfR), and it documents contrasting impacts of nitrate (NO3-) on BrO3- reduction, as well as formation of poly-β-hydroxybutyrate (PHB), an internal C- and electron-storage material. When the electron donor, CH4, was in ample supply, NO3- enhanced BrO3- reduction by stimulating the growth of denitrifying bacteria ( Meiothermus, Comamonadaceae, and Anaerolineaceae) able to reduce BrO3- and NO3- simultaneously. This was supported by increases in denitrifying enzymes (e.g., nitrate reductase, nitrite reductase, nitrous-oxide reductase, and nitric-oxide reductase) through quantitative polymerase chain reaction (qPCR) analysis and metagenomic prediction of these functional genes. When the electron donor was in limited supply, NO3- was the preferred electron acceptor over BrO3- due to competition for the common electron donor; this was supported by the significant oxidation of stored PHB when NO3- was high enough to cause electron-donor limitation. Methanotrophs (e.g., Methylocystis, Methylomonas, and genera within Comamonadaceae) were implicated as the main PHB producers in the biofilms, and their ability to oxidize PHB mitigated the impacts of competition for CH4.
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Affiliation(s)
- Chun-Yu Lai
- College of Environmental and Resource Science , Zhejiang University , Hangzhou 310027 , China
| | - Pan-Long Lv
- College of Environmental and Resource Science , Zhejiang University , Hangzhou 310027 , China
| | - Qiu-Yi Dong
- College of Environmental and Resource Science , Zhejiang University , Hangzhou 310027 , China
| | - Shi Lei Yeo
- College of Environmental and Resource Science , Zhejiang University , Hangzhou 310027 , China
| | - Bruce E Rittmann
- Biodesign Swette Center for Environmental Biotechnology , Arizona State University , P.O. Box 875701, Tempe , Arizona 85287-5701 , United States
| | - He-Ping Zhao
- College of Environmental and Resource Science , Zhejiang University , Hangzhou 310027 , China
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