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de Leeuw KD, van Willigen MJW, Vrauwdeunt T, Strik DPPTB. CO 2 supply is a powerful tool to control homoacetogenesis, chain elongation and solventogenesis in ethanol and carboxylate fed reactor microbiomes. Front Bioeng Biotechnol 2024; 12:1329288. [PMID: 38720876 PMCID: PMC11076876 DOI: 10.3389/fbioe.2024.1329288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2023] [Accepted: 03/25/2024] [Indexed: 05/12/2024] Open
Abstract
Anaerobic fermentation technology enables the production of medium chain carboxylates and alcohols through microbial chain elongation. This involves steering reactor microbiomes to yield desired products, with CO2 supply playing a crucial role in controlling ethanol-based chain elongation and facilitating various bioprocesses simultaneously. In the absence of CO2 supply (Phase I), chain elongation predominantly led to n-caproate with a high selectivity of 96 Cmol%, albeit leaving approximately 80% of ethanol unconverted. During this phase, C. kluyveri and Proteiniphilum-related species dominated the reactors. In Phase II, with low CO2 input (2.0 NmL L-1 min-1), formation of n-butyrate, butanol, and hexanol was stimulated. Increasing CO2 doses in Phase III (6 NmL L-1 min-1) led to CO2 utilization via homoacetogenesis, coinciding with the enrichment of Clostridium luticellarii, a bacterium that can use CO2 as an electron acceptor. Lowering CO2 dose to 0.5 NmL L-1 min-1 led to a shift in microbiome composition, diminishing the dominance of C. luticellarii while increasing C. kluyveri abundance. Additionally, other Clostridia, Proteiniphilum, and Lactobacillus sakei-related species became prevalent. This decrease in CO2 load from 6 to 0.5 NmL L-1 min-1 minimized excessive ethanol oxidation from 30%-50% to 0%-3%, restoring a microbiome favoring net n-butyrate consumption and n-caproate production. The decreased ethanol oxidation coincided with the resurgence of hydrogen formation at partial pressures above 1%. High concentrations of butyrate, caproate, and ethanol in the reactor, along with low acetate concentration, promoted the formation of butanol and hexanol. It is evident that CO2 supply is indispensable for controlling chain elongation in an open culture and it can be harnessed to stimulate higher alcohol formation or induce CO2 utilization as an electron acceptor.
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Affiliation(s)
- Kasper D. de Leeuw
- Environmental Technology, Wageningen University and Research, Wageningen, Netherlands
- ChainCraft B.V., Amsterdam, Netherlands
| | | | - Ton Vrauwdeunt
- Environmental Technology, Wageningen University and Research, Wageningen, Netherlands
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Villegas-Rodríguez SB, Arreola-Vargas J, Buitrón G. Influence of pH and temperature on the performance and microbial community during the production of medium-chain carboxylic acids using winery effluents as substrate. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2024:10.1007/s11356-024-33103-5. [PMID: 38558339 DOI: 10.1007/s11356-024-33103-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Accepted: 03/22/2024] [Indexed: 04/04/2024]
Abstract
Winery effluents containing high ethanol concentrations and diverse organic matter are ideal substrates for producing medium-chain carboxylic acids via fermentation and chain elongation. However, the process needs to be better understood. This study presents novel insights into the bioconversion mechanisms of medium-chain carboxylic acids by correlating fermentation and chain elongation kinetic profiles with the study of microbial communities at different pH (5 to 7) conditions and temperatures (30 to 40 °C). It was found that high productivities of MCCA were obtained using a native culture and winery effluents as a natural substrate. Minor pH variations significantly affected the metabolic pathway of the microorganisms for MCCA production. The maximal productivities of hexanoic (715 mg/L/d) and octanoic (350 mg/L/d) acids were found at pH 6 and 35 °C. Results evidence that the presence of Clostridium, Bacteroides, and Negativicutes promotes the high productions of MCCA. The formation of heptanoic acid was favor when Mogibacterium and Burkholderia were present.
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Affiliation(s)
- Sharon B Villegas-Rodríguez
- Laboratory for Research On Advanced Processes for Water Treatment, Unidad Académica Juriquilla, Instituto de Ingeniería, Universidad Nacional Autónoma de México, Blvd. Juriquilla 3001, 76230, Queretaro, Mexico
| | - Jorge Arreola-Vargas
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX, 77843, USA
| | - Germán Buitrón
- Laboratory for Research On Advanced Processes for Water Treatment, Unidad Académica Juriquilla, Instituto de Ingeniería, Universidad Nacional Autónoma de México, Blvd. Juriquilla 3001, 76230, Queretaro, Mexico.
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Montecchio D, Gazzola G, Gallipoli A, Gianico A, Braguglia CM. Medium chain Fatty acids production from Food Waste via homolactic fermentation and lactate/ethanol elongation: Electron balance and thermodynamic assessment. WASTE MANAGEMENT (NEW YORK, N.Y.) 2024; 177:289-297. [PMID: 38359509 DOI: 10.1016/j.wasman.2024.01.049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 01/08/2024] [Accepted: 01/29/2024] [Indexed: 02/17/2024]
Abstract
This study explored the potential of Food Waste (FW) extract as a suitable substrate for Medium Chain Fatty Acids (MCFAs) production, in a single-phase reactor, where both fermentation and Chain Elongation (CE) processes occurred simultaneously. A continuous experiment was conducted with an Organic Loading Rate (OLR) = 20 gCOD L-1 d-1 and was fed in batch mode twice a week with pH = 6. In addition, four batch tests were performed, to assess the effects on the MCFAs production of caproate inhibition, hydrogen partial pressure (PH2) and different lactate/acetate ratios. Thermodynamics and electron flux were calculated to gain insights into the process pathways. Due to the presence of aminoacids, fermentation was mostly homolactic and both lactate and ethanol were produced as Electron Donors (EDs); the average MCFAs production efficiency was ∼ 12 %, although after 4 weeks the elongation process was halted, resulting in EDs accumulation. This occurred regardless of inoculum selection and the presence of caproate as a possible inhibitor, suggesting that EDs accumulation was due to the elongation process kinetics being slower than those of the fermentation step, thus calling for a longer Hydraulic Retention Time (HRT). It's worth noting that lactate was prevalently self-elongated to butyrate, whereas ethanol elongation only took place after lactate depletion, but was more efficient since it required other Electron Acceptors (EAs) such as butyrate, propionate or valerate. Moreover, the selected pH limited the acrylate pathway to a reasonable extent, whereas the high PH2 prevented both ethanol and lactate oxydation to acetate.
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Affiliation(s)
- Daniele Montecchio
- Istituto di Ricerca sulle Acque-CNR, Area della Ricerca RM1, 00015 Monterotondo, Roma, Italy.
| | - Giulio Gazzola
- Istituto di Ricerca sulle Acque-CNR, Area della Ricerca RM1, 00015 Monterotondo, Roma, Italy.
| | - Agata Gallipoli
- Istituto di Ricerca sulle Acque-CNR, Area della Ricerca RM1, 00015 Monterotondo, Roma, Italy.
| | - Andrea Gianico
- Istituto di Ricerca sulle Acque-CNR, Area della Ricerca RM1, 00015 Monterotondo, Roma, Italy.
| | - Camilla M Braguglia
- Istituto di Ricerca sulle Acque-CNR, Area della Ricerca RM1, 00015 Monterotondo, Roma, Italy.
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Chen R, Ji X, Chen Z, Huang L, Zhu J. Regulation of hydraulic retention time on caproic acid production via two-phase anaerobic fermentation of Chinese cabbage waste with autopoietic electron donors. J Biotechnol 2024; 381:1-10. [PMID: 38176540 DOI: 10.1016/j.jbiotec.2023.12.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Revised: 11/28/2023] [Accepted: 12/23/2023] [Indexed: 01/06/2024]
Abstract
The effects of hydraulic retention time (HRT) on the performance of two-phase anaerobic fermentation for caproic acid production from Chinese cabbage waste (CCW) were investigated. In the electron donor phase, yeast was inoculated to achieve efficient autopoietic ethanol, providing electron donors for the chain elongation process. Shorter HRT led to drastic fluctuations in microorganisms, thus resulting in lower acid yields at HRT of 6 days. At HRT of 10 days, the balanced collaboration of various key bacteria avoided the accumulation of intermediate by-products, and the caproic acid production reached 4660 mg COD/L, which was 119.5% and 154.8% higher than that at HRTs of 6 and 14 days, respectively. At HRT of 14 days, the low ethanol loading rate resulted in ethanol excessive-oxidation to acetic acid. Acetic acid accounted for 41.5% of the total product, while the selectivity of caproic acid was only 15.3%. The main contributor to the production process of caproic acid was Caproiciproducens, while the Ruminalococcaceae also played a role in the process. This study provided a theoretical basis for the efficient production of caproic acid through continuous fermentation with autopoietic electron donors.
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Affiliation(s)
- Ranran Chen
- School of Agricultural Engineering and Food Science, Shandong University of Technology, Zibo, 255000, China
| | - Xiaofeng Ji
- School of Agricultural Engineering and Food Science, Shandong University of Technology, Zibo, 255000, China
| | - Zhengang Chen
- School of Agricultural Engineering and Food Science, Shandong University of Technology, Zibo, 255000, China
| | - Liu Huang
- School of Agricultural Engineering and Food Science, Shandong University of Technology, Zibo, 255000, China
| | - Jiying Zhu
- School of Agricultural Engineering and Food Science, Shandong University of Technology, Zibo, 255000, China.
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Gallipoli A, Angelini F, Angelini S, Braguglia CM, Montecchio D, Tonanzi B, Gianico A. Thermally enhanced solid-liquid separation process in food waste biorefinery: modelling the anaerobic digestion of solid residues. Front Bioeng Biotechnol 2024; 12:1343396. [PMID: 38371422 PMCID: PMC10869513 DOI: 10.3389/fbioe.2024.1343396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Accepted: 01/18/2024] [Indexed: 02/20/2024] Open
Abstract
The biochemical valorization potential of food waste (FW) could be exploited by extracting decreasing added-value bio-based products and converting the final residues into energy. In this context, multi-purpose and versatile schemes integrating thermal and biochemical conversion processes will play a key role. An upstream thermal pretreatment + solid-liquid separation unit was here proposed to optimize the conversion of the liquid fraction of FW into valuable chemicals through semi-continuous fermentation process, and the conversion of the residual solid fraction into biomethane through anaerobic digestion. The solid residues obtained after thermal pretreatment presented a higher soluble COD fraction, which resulted in higher methane production with respect to the raw residues (0.33 vs. 0.29 Nm3CH4 kg-1VSfed) and higher risk of acidification and failure of methanogenesis when operating at lower HRT (20d). On the contrary, at HRT = 40 d, the pretreatment did not affect the methane conversion rates and both tests evidenced similar methane productions of 0.33 Nm3CH4 kg-1VSfed. In the reactor fed with pretreated residue, the association of hydrogenotrophic methanogens with syntrophic bacteria prevented the acidification of the system. Modelling proved the eligibility of the FW solid residues as substrates for anaerobic digestion, given their small inert fractions that ranged between 0% and 30% of the total COD content.
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Affiliation(s)
| | | | | | | | | | | | - Andrea Gianico
- National Research Council of Italy, Water Research Institute, CNR-IRSA, Rome, Italy
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Ulčar B, Regueira A, Podojsteršek M, Boon N, Ganigué R. Why do lactic acid bacteria thrive in chain elongation microbiomes? Front Bioeng Biotechnol 2024; 11:1291007. [PMID: 38274012 PMCID: PMC10809155 DOI: 10.3389/fbioe.2023.1291007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Accepted: 12/11/2023] [Indexed: 01/27/2024] Open
Abstract
Efficient waste management is necessary to transition towards a more sustainable society. An emerging trend is to use mixed culture biotechnology to produce chemicals from organic waste. Insights into the metabolic interactions between community members and their growth characterization are needed to mediate knowledge-driven bioprocess development and optimization. Here, a granular sludge bioprocess for the production of caproic acid through sugar-based chain elongation metabolism was established. Lactic acid and chain-elongating bacteria were identified as the two main functional guilds in the granular community. The growth features of the main community representatives (isolate Limosilactobacillus musocae G03 for lactic acid bacteria and type strain Caproiciproducens lactatifermentans for chain-elongating bacteria) were characterized. The measured growth rates of lactic acid bacteria (0.051 ± 0.005 h-1) were two times higher than those of chain-elongating bacteria (0.026 ± 0.004 h-1), while the biomass yields of lactic acid bacteria (0.120 ± 0.005 g biomass/g glucose) were two times lower than that of chain-elongating bacteria (0.239 ± 0.007 g biomass/g glucose). This points towards differential growth strategies, with lactic acid bacteria resembling that of a r-strategist and chain-elongating bacteria resembling that of a K-strategist. Furthermore, the half-saturation constant of glucose for L. mucosae was determined to be 0.35 ± 0.05 g/L of glucose. A linear trend of caproic acid inhibition on the growth of L. mucosae was observed, and the growth inhibitory caproic acid concentration was predicted to be 13.6 ± 0.5 g/L, which is the highest reported so far. The pre-adjustment of L. mucosae to 4 g/L of caproic acid did not improve the overall resistance to it, but did restore the growth rates at low caproic acid concentrations (1-4 g/L) to the baseline values (i.e., growth rate at 0 g/L of caproic acid). High resistance to caproic acid enables lactic acid bacteria to persist and thrive in the systems intended for caproic acid production. Here, insights into the growth of two main functional guilds of sugar-based chain elongation systems are provided which allows for a better understanding of their interactions and promotes future bioprocess design and optimization.
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Affiliation(s)
- Barbara Ulčar
- Center for Microbial Ecology and Technology (CMET), Department of Biotechnology, Ghent University, Gent, Belgium
- Center for Advanced Process Technology for Urban Resource Recovery (CAPTURE), Gent, Belgium
| | - Alberte Regueira
- Center for Microbial Ecology and Technology (CMET), Department of Biotechnology, Ghent University, Gent, Belgium
- Center for Advanced Process Technology for Urban Resource Recovery (CAPTURE), Gent, Belgium
- Department of Chemical Engineering, Universidade de Santiago de Compostela, Santiago de Compostela, Spain
| | - Maja Podojsteršek
- Center for Microbial Ecology and Technology (CMET), Department of Biotechnology, Ghent University, Gent, Belgium
- Center for Advanced Process Technology for Urban Resource Recovery (CAPTURE), Gent, Belgium
| | - Nico Boon
- Center for Microbial Ecology and Technology (CMET), Department of Biotechnology, Ghent University, Gent, Belgium
- Center for Advanced Process Technology for Urban Resource Recovery (CAPTURE), Gent, Belgium
| | - Ramon Ganigué
- Center for Microbial Ecology and Technology (CMET), Department of Biotechnology, Ghent University, Gent, Belgium
- Center for Advanced Process Technology for Urban Resource Recovery (CAPTURE), Gent, Belgium
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7
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Sabbe K, D'Haen L, Boon N, Ganigué R. Predicting the performance of chain elongating microbiomes through flow cytometric fingerprinting. WATER RESEARCH 2023; 243:120323. [PMID: 37459796 DOI: 10.1016/j.watres.2023.120323] [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: 03/23/2023] [Revised: 06/29/2023] [Accepted: 07/06/2023] [Indexed: 09/07/2023]
Abstract
As part of the circular bio-economy paradigm shift, waste management and valorisation practices have moved away from sanitation and towards the production of added-value compounds. Recently, the development of mixed culture bioprocess for the conversion of waste(water) to platform chemicals, such as medium chain carboxylic acids, has attracted significant interest. Often, the microbiology of these novel bioprocesses is less diverse and more prone to disturbances, which can lead to process failure. This issue can be tackled by implementing an advanced monitoring strategy based on the microbiology of the process. In this study, flow cytometry was used to monitor the microbiology of lactic acid chain elongation for the production of caproic acid, and assess its performance both qualitatively and quantitatively. Two continuous stirred tank reactors for chain elongation were monitored flow cytometrically for over 336 days. Through community typing, four specific community types could be identified and correlated to both a specific functionality and genotypic diversity. Additionally, the machine-learning algorithms trained in this study demonstrated the ability to predict production rates of, amongst others, caproic acid with high accuracy in the present (R² > 0.87) and intermediate accuracy in the near future (R² > 0.63). The identification of specific community types and the development of predictive algorithms form the basis of advanced bioprocess monitoring based on flow cytometry, and have the potential to improve bioprocess control and optimization, leading to better product quality and yields.
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Affiliation(s)
- Kevin Sabbe
- Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, 9000 Ghent, Belgium; Center for Advanced Process Technology for Urban Resource Recovery (CAPTURE), Frieda Saeysstraat 1, 9052 Ghent, Belgium
| | - Liese D'Haen
- Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, 9000 Ghent, Belgium
| | - Nico Boon
- Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, 9000 Ghent, Belgium; Center for Advanced Process Technology for Urban Resource Recovery (CAPTURE), Frieda Saeysstraat 1, 9052 Ghent, Belgium
| | - Ramon Ganigué
- Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, 9000 Ghent, Belgium; Center for Advanced Process Technology for Urban Resource Recovery (CAPTURE), Frieda Saeysstraat 1, 9052 Ghent, Belgium.
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8
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Crognale S, Massimi A, Sbicego M, Braguglia CM, Gallipoli A, Gazzola G, Gianico A, Tonanzi B, Di Pippo F, Rossetti S. Ecology of food waste chain-elongating microbiome. Front Bioeng Biotechnol 2023; 11:1157243. [PMID: 37113665 PMCID: PMC10126515 DOI: 10.3389/fbioe.2023.1157243] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Accepted: 03/31/2023] [Indexed: 04/29/2023] Open
Abstract
Microbial chain elongation has emerged as a valuable bioprocess for obtaining marketable products, such as medium chain fatty acids usable in several industrial applications, from organic waste. The understanding of the microbiology and microbial ecology in these systems is crucial to apply these microbiomes in reliable production processes controlling microbial pathways to promote favourable metabolic processes, which will in turn increase product specificity and yields. In this research, the dynamics, cooperation/competition and potentialities of bacterial communities involved in the long-term lactate-based chain elongation process from food waste extract were evaluated under different operating conditions by DNA/RNA amplicon sequencing and functional profile prediction. The feeding strategies and the applied organic loading rates strongly affected the microbial community composition. The use of food waste extract promoted the selection of primary fermenters (i.e., Olsenella, Lactobacillus) responsible for the in situ production of electron donors (i.e., lactate). The discontinuous feeding and the organic loading rate 15 gCOD L-1 d-1 selected the best performing microbiome in which microbes coexist and cooperate to complete the chain elongation process. Both at DNA and RNA level, this microbiome was composed by the lactate producer Olsenella, the short chain fatty acids producers Anaerostipes, Clostridium sensu stricto 7, C. sensu stricto 12, Corynebacterium, Erysipelotrichaceae UCG-004, F0332, Leuconostoc, and the chain elongator Caproiciproducens. This microbiome also showed the highest predicted abundance of short-chain acyl-CoA dehydrogenase, the functional enzyme responsible for the chain elongation process. The combined approach herein used allowed to study the microbial ecology of chain elongation process from food waste by identifying the main functional groups, establishing the presence of potential biotic interactions within the microbiomes, and predicting metabolic potentialities. This study provided pivotal indications for the selection of high-performance microbiome involved in caproate production from food waste that can serve as a basis for further improving system performance and engineering the process scale-up.
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Gazzola G, Maria Braguglia C, Crognale S, Gallipoli A, Mininni G, Piemonte V, Rossetti S, Tonanzi B, Gianico A. Biorefining food waste through the anaerobic conversion of endogenous lactate into caproate: A fragile balance between microbial substrate utilization and product inhibition. WASTE MANAGEMENT (NEW YORK, N.Y.) 2022; 150:328-338. [PMID: 35907330 DOI: 10.1016/j.wasman.2022.07.031] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 06/27/2022] [Accepted: 07/21/2022] [Indexed: 06/15/2023]
Abstract
New technologies development and renewable source exploitation are key tools to realize the European Green Deal and to boost the bio-based economy. In this context, fermentation of organic residues as food waste is an efficient method to obtain marketable products such as carboxylic acids widely applied in industrial production. Under favourable thermodynamic conditions, short chain fatty acids deriving from primary fermentation could be biologically converted into medium-chain fatty acids as caproate via chain elongation (CE) process, by using ethanol or lactate as electron donors. This study evaluates the effectivity of producing caproate from Food Waste extract rich in organics with in situ electron donor production. The test carried out at OLR 15 gCOD L-1d-1 showed high Volatile Fatty Acids (from acetic to caproic acid) yields (0.37 g g-1CODfed), with a maximum caproate concentration of 8 g L-1. The associated microbiome was composed by lactate-producing bacteria (Corynebacterium, Lactobacillus, and Olsenella) and by chain elongators (Clostridiaceae and Caproiciproducens). By stressing the system with OLR increase up to 20 gCOD L-1d-1, the CE process was inhibited by the high concentration of caproate (low occurrence of Clostridiaceae and Caproiciproducens). Nevertheless, after few days of stop-feeding regime imposed to the system, the microbiome restored its capability to proceed with lactate-based CE pathways. Different batch tests carried out with the inhibited biomass at increasing initial caproate concentration confirmed its impact on lactate utilization kinetics.
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Affiliation(s)
- Giulio Gazzola
- Water Research Institute, National Research Council of Italy, CNR-IRSA, Area della Ricerca RM1, Via Salaria km 29.300, 00015 Monterotondo, Roma, Italy
| | - Camilla Maria Braguglia
- Water Research Institute, National Research Council of Italy, CNR-IRSA, Area della Ricerca RM1, Via Salaria km 29.300, 00015 Monterotondo, Roma, Italy
| | - Simona Crognale
- Water Research Institute, National Research Council of Italy, CNR-IRSA, Area della Ricerca RM1, Via Salaria km 29.300, 00015 Monterotondo, Roma, Italy
| | - Agata Gallipoli
- Water Research Institute, National Research Council of Italy, CNR-IRSA, Area della Ricerca RM1, Via Salaria km 29.300, 00015 Monterotondo, Roma, Italy
| | - Giuseppe Mininni
- Water Research Institute, National Research Council of Italy, CNR-IRSA, Area della Ricerca RM1, Via Salaria km 29.300, 00015 Monterotondo, Roma, Italy
| | - Vincenzo Piemonte
- Faculty of Engineering, University Campus Bio-Medico, Via Alvaro del Portillo, 21, 00128 Roma, Italy
| | - Simona Rossetti
- Water Research Institute, National Research Council of Italy, CNR-IRSA, Area della Ricerca RM1, Via Salaria km 29.300, 00015 Monterotondo, Roma, Italy
| | - Barbara Tonanzi
- Water Research Institute, National Research Council of Italy, CNR-IRSA, Area della Ricerca RM1, Via Salaria km 29.300, 00015 Monterotondo, Roma, Italy
| | - Andrea Gianico
- Water Research Institute, National Research Council of Italy, CNR-IRSA, Area della Ricerca RM1, Via Salaria km 29.300, 00015 Monterotondo, Roma, Italy.
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Intensification of Acidogenic Fermentation for the Production of Biohydrogen and Volatile Fatty Acids—A Perspective. FERMENTATION-BASEL 2022. [DOI: 10.3390/fermentation8070325] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Utilising ‘wastes’ as ‘resources’ is key to a circular economy. While there are multiple routes to waste valorisation, anaerobic digestion (AD)—a biochemical means to breakdown organic wastes in the absence of oxygen—is favoured due to its capacity to handle a variety of feedstocks. Traditional AD focuses on the production of biogas and fertiliser as products; however, such low-value products combined with longer residence times and slow kinetics have paved the way to explore alternative product platforms. The intermediate steps in conventional AD—acidogenesis and acetogenesis—have the capability to produce biohydrogen and volatile fatty acids (VFA) which are gaining increased attention due to the higher energy density (than biogas) and higher market value, respectively. This review hence focusses specifically on the production of biohydrogen and VFAs from organic wastes. With the revived interest in these products, a critical analysis of recent literature is needed to establish the current status. Therefore, intensification strategies in this area involving three main streams: substrate pre-treatment, digestion parameters and product recovery are discussed in detail based on literature reported in the last decade. The techno-economic aspects and future pointers are clearly highlighted to drive research forward in relevant areas.
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11
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De Groof V, Coma M, Arnot T, Leak DJ, Lanham AB. Selecting fermentation products for food waste valorisation with HRT and OLR as the key operational parameters. WASTE MANAGEMENT (NEW YORK, N.Y.) 2021; 127:80-89. [PMID: 33932853 DOI: 10.1016/j.wasman.2021.04.023] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 03/29/2021] [Accepted: 04/10/2021] [Indexed: 06/12/2023]
Abstract
Acidogenic fermentation is attractive for food waste valorisation. A better understanding is required on how operation affects product selectivity. This study demonstrated that the hydraulic retention time (HRT) and organic loading rate (OLR) selected fermentation pathways in a single-stage, semi-continuous stirred tank reactor. Three combinations of HRT and OLR were tested to distinguish the effect of each parameter. Three fermentation profiles with distinct microbial communities were obtained. Predominantly n-butyric acid (13 ± 2 gCOD L-1, 55 ± 14% of carboxylates) was produced at an HRT of 8.5 days and OLR around 12 gCOD L-1d-1. Operating at an HRT two days longer, yet with similar OLR, stimulated chain elongation (up to 13.6 gCOD L-1 of n-caproic acid). This was reflected by a microbial community twice as diverse at longer HRT as indicated by first and second order Hill number (1D = 24 ± 4, 2D = 12 ± 3) and by a higher relative abundance of genera related to secondary fermentation, such as the VFA-elongating Caproiciproducens spp., and secondary lactic acid fermenter Secundilactobacillus spp.. Operating at a higher OLR (20 gCOD L-1d-1) but HRT of 8.5 days, resulted in typical lactic acid fermentation (34 ± 5 gCOD L-1) harbouring a less diverse community (1D = 8.0 ± 0.7, 2D = 5.7 ± 0.9) rich in acid-resistant homofermentative Lactobacillus spp. These findings demonstrate that a flexible product portfolio can be achieved by small adjustments in two key operating conditions. This improves the economic potential of acidogenic fermentation for food waste valorisation.
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Affiliation(s)
- Vicky De Groof
- EPSRC Centre for Doctoral Training in Sustainable Chemical Technologies, University of Bath, Claverton Down, Bath BA2 7AY, UK; Department of Chemical Engineering, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - Marta Coma
- Centre for Sustainable and Circular Technologies (CSCT), University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - Tom Arnot
- Department of Chemical Engineering, University of Bath, Claverton Down, Bath BA2 7AY, UK; Centre for Sustainable and Circular Technologies (CSCT), University of Bath, Claverton Down, Bath BA2 7AY, UK; Water Innovation & Research Centre (WIRC), University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - David J Leak
- Centre for Sustainable and Circular Technologies (CSCT), University of Bath, Claverton Down, Bath BA2 7AY, UK; Water Innovation & Research Centre (WIRC), University of Bath, Claverton Down, Bath BA2 7AY, UK; Department of Biology & Biochemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - Ana B Lanham
- Department of Chemical Engineering, University of Bath, Claverton Down, Bath BA2 7AY, UK; Water Innovation & Research Centre (WIRC), University of Bath, Claverton Down, Bath BA2 7AY, UK.
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Baleeiro FCF, Kleinsteuber S, Sträuber H. Hydrogen as a Co-electron Donor for Chain Elongation With Complex Communities. Front Bioeng Biotechnol 2021; 9:650631. [PMID: 33898406 PMCID: PMC8059637 DOI: 10.3389/fbioe.2021.650631] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Accepted: 03/12/2021] [Indexed: 01/04/2023] Open
Abstract
Electron donor scarcity is seen as one of the major issues limiting economic production of medium-chain carboxylates from waste streams. Previous studies suggest that co-fermentation of hydrogen in microbial communities that realize chain elongation relieves this limitation. To better understand how hydrogen co-feeding can support chain elongation, we enriched three different microbial communities from anaerobic reactors (A, B, and C with ascending levels of diversity) for their ability to produce medium-chain carboxylates from conventional electron donors (lactate or ethanol) or from hydrogen. In the presence of abundant acetate and CO2, the effects of different abiotic parameters (pH values in acidic to neutral range, initial acetate concentration, and presence of chemical methanogenesis inhibitors) were tested along with the enrichment. The presence of hydrogen facilitated production of butyrate by all communities and improved production of i-butyrate and caproate by the two most diverse communities (B and C), accompanied by consumption of acetate, hydrogen, and lactate/ethanol (when available). Under optimal conditions, hydrogen increased the selectivity of conventional electron donors to caproate from 0.23 ± 0.01 mol e-/mol e- to 0.67 ± 0.15 mol e-/mol e- with a peak caproate concentration of 4.0 g L-1. As a trade-off, the best-performing communities also showed hydrogenotrophic methanogenesis activity by Methanobacterium even at high concentrations of undissociated acetic acid of 2.9 g L-1 and at low pH of 4.8. According to 16S rRNA amplicon sequencing, the suspected caproate producers were assigned to the family Anaerovoracaceae (Peptostreptococcales) and the genera Megasphaera (99.8% similarity to M. elsdenii), Caproiciproducens, and Clostridium sensu stricto 12 (97-100% similarity to C. luticellarii). Non-methanogenic hydrogen consumption correlated to the abundance of Clostridium sensu stricto 12 taxa (p < 0.01). If a robust methanogenesis inhibition strategy can be found, hydrogen co-feeding along with conventional electron donors can greatly improve selectivity to caproate in complex communities. The lessons learned can help design continuous hydrogen-aided chain elongation bioprocesses.
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Affiliation(s)
- Flávio C F Baleeiro
- Department of Environmental Microbiology, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany.,Technical Biology, Institute of Process Engineering in Life Science II, Karlsruhe Institute of Technology - KIT, Karlsruhe, Germany
| | - Sabine Kleinsteuber
- Department of Environmental Microbiology, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany
| | - Heike Sträuber
- Department of Environmental Microbiology, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany
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Direct Conversion of Food Waste Extract into Caproate: Metagenomics Assessment of Chain Elongation Process. Microorganisms 2021; 9:microorganisms9020327. [PMID: 33562834 PMCID: PMC7915914 DOI: 10.3390/microorganisms9020327] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Revised: 02/01/2021] [Accepted: 02/03/2021] [Indexed: 12/30/2022] Open
Abstract
In a circular economy strategy, waste resources can be used for the biological production of high added-value substances, such as medium chain fatty acids (MCFAs), thus minimising waste and favouring a sustainable process. This study investigates single-stage fermentation processes for the production of MCFAs in a semi-continuous reactor treating the extract of real food waste (FW), without the addition of external electron donors. Two sequential acidogenic fermentation tests were carried out at an organic loading rate (OLR) of 5 and 15 gCOD L−1d−1 with a hydraulic retention time of 4 days and pH controlled at 6 ± 0.2. The highest level of caproate (4.8 g L−1) was observed at OLR of 15 gCOD L−1d−1 with a microbiome mainly composed by lactate-producing Actinomyces, Atopobium, and Olsenella species and caproate-producing Pseudoramibacter. Metagenomic analysis revealed the presence of key enzymes for the production of lactate, such as lactate dehydrogenase and pyruvate ferredoxin oxidoreductase, as well as several enzymes involved in the reverse β-oxidation pathway, thus suggesting the occurrence of a lactate-based chain elongation process.
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Candry P, Ganigué R. Chain elongators, friends, and foes. Curr Opin Biotechnol 2021; 67:99-110. [PMID: 33529974 DOI: 10.1016/j.copbio.2021.01.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2020] [Revised: 01/02/2021] [Accepted: 01/07/2021] [Indexed: 12/14/2022]
Abstract
Bioproduction of medium chain carboxylic acids has recently emerged as an alternative strategy to valorize low-value organic waste and side-streams. Key to this route is chain elongation, an anaerobic microbial process driven by ethanol, lactic acid, or carbohydrates. Because these technologies use wastes as feedstocks, mixed microbial communities are often considered as biocatalysts. Understanding and steering these microbiomes is key to optimize bioprocess performance. From a meta-analysis of publicly available sequencing data, we (i) explore how the current collection of isolated chain elongators compares to microbiome members, (ii) discuss the main beneficial and antagonistic interactions with community partners, and (iii) identify the key research gaps and needs to help understand chain elongation microbiomes, and design/steer these novel bioproduction processes.
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Affiliation(s)
- Pieter Candry
- Civil and Environmental Engineering, University of Washington, 201 More Hall, Box 352700, Seattle, WA 98195-2700, USA
| | - Ramon Ganigué
- Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, 9000 Ghent, Belgium.
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