1
|
Gu X, Sun J, Wang T, Li J, Wang H, Wang J, Wang Y. Comprehensive review of microbial production of medium-chain fatty acids from waste activated sludge and enhancement strategy. BIORESOURCE TECHNOLOGY 2024; 402:130782. [PMID: 38701982 DOI: 10.1016/j.biortech.2024.130782] [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: 03/02/2024] [Revised: 04/30/2024] [Accepted: 04/30/2024] [Indexed: 05/06/2024]
Abstract
Microbial production of versatile applicability medium-chain fatty acids (MCFAs) (C6-C10) from waste activated sludge (WAS) provides a pioneering approach for wastewater treatment plants (WWTPs) to achieve carbon recovery. Mounting studies emerged endeavored to promote the MCFAs production from WAS while struggling with limited MCFAs production and selectivity. Herein, this review covers comprehensive introduction of the transformation process from WAS to MCFAs and elaborates the mechanisms for unsatisfactory MCFAs production. The enhancement strategies for biotransformation of WAS to MCFAs was presented. Especially, the robust performance of iron-based materials is highlighted. Furthermore, knowledge gaps are identified to outline future research directions. Recycling MCFAs from WAS presents a promising option for future WAS treatment, with iron-based materials emerging as a key regulatory strategy in advancing the application of WAS-to-MCFAs biotechnology. This review will advance the understanding of MCFAs recovery from WAS and promote sustainable resource management in WWTPs.
Collapse
Affiliation(s)
- Xin Gu
- State Key Laboratory of Pollution Control and Resources Reuse, Shanghai Institute of Pollution Control and Ecological Security, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
| | - Jing Sun
- State Key Laboratory of Pollution Control and Resources Reuse, Shanghai Institute of Pollution Control and Ecological Security, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
| | - Tong Wang
- State Key Laboratory of Pollution Control and Resources Reuse, Shanghai Institute of Pollution Control and Ecological Security, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
| | - Jia Li
- State Key Laboratory of Pollution Control and Resources Reuse, Shanghai Institute of Pollution Control and Ecological Security, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
| | - Han Wang
- State Key Laboratory of Pollution Control and Resources Reuse, Shanghai Institute of Pollution Control and Ecological Security, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
| | - Jialin Wang
- State Key Laboratory of Pollution Control and Resources Reuse, Shanghai Institute of Pollution Control and Ecological Security, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
| | - Yayi Wang
- State Key Laboratory of Pollution Control and Resources Reuse, Shanghai Institute of Pollution Control and Ecological Security, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
| |
Collapse
|
2
|
Liu Y, Chen L, Duan Y, Li R, Yang Z, Liu S, Li G. Recent progress and prospects for chain elongation of transforming biomass waste into medium-chain fatty acids. CHEMOSPHERE 2024; 355:141823. [PMID: 38552798 DOI: 10.1016/j.chemosphere.2024.141823] [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: 02/04/2024] [Revised: 03/18/2024] [Accepted: 03/26/2024] [Indexed: 04/06/2024]
Abstract
Chain elongation technology utilises microorganisms in anaerobic digestion to transform waste biomass into medium-chain fatty acids that have greater economic value. This innovative technology expands upon traditional anaerobic digestion methods, requiring abundant substrates that serve as electron donors and acceptors, and inoculating microorganisms with chain elongation functions. While this process may result in the production of by-products and elicit competitive responses, toxicity suppression of microorganisms by substrates and products remains a significant obstacle to the industrialisation of chain elongation technology. This study provides a comprehensive overview of existing research on widely employed electron donors and their synthetic reactions, competitive reactions, inoculum selection, toxicity inhibition of substrates and products, and increased chain elongation approaches. Additionally, it presents actionable recommendations for future research and development endeavours in this domain, intending to inspire and guide researchers in advancing the frontiers of chain elongation technology.
Collapse
Affiliation(s)
- Yuhao Liu
- School of Environmental and Municipal Engineering, North China University of Water Resources and Electric Power, Zhengzhou, 450046, Henan Province, China.
| | - Long Chen
- School of Environmental and Municipal Engineering, North China University of Water Resources and Electric Power, Zhengzhou, 450046, Henan Province, China
| | - Yacong Duan
- School of Environmental and Municipal Engineering, North China University of Water Resources and Electric Power, Zhengzhou, 450046, Henan Province, China
| | - Ruihua Li
- School of Environmental and Municipal Engineering, North China University of Water Resources and Electric Power, Zhengzhou, 450046, Henan Province, China
| | - Ziyan Yang
- School of Environmental and Municipal Engineering, North China University of Water Resources and Electric Power, Zhengzhou, 450046, Henan Province, China
| | - Shuli Liu
- School of Environmental and Municipal Engineering, North China University of Water Resources and Electric Power, Zhengzhou, 450046, Henan Province, China
| | - Guoting Li
- School of Environmental and Municipal Engineering, North China University of Water Resources and Electric Power, Zhengzhou, 450046, Henan Province, China
| |
Collapse
|
3
|
Chen Z, Shi Z, Zhang Y, Shi Y, Sun M, Cui Y, Zhang S, Luo G. Metagenomic analysis towards understanding the effects of ammonia on chain elongation process for medium chain fatty acids production. BIORESOURCE TECHNOLOGY 2024; 395:130413. [PMID: 38310979 DOI: 10.1016/j.biortech.2024.130413] [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: 12/26/2023] [Revised: 01/29/2024] [Accepted: 01/30/2024] [Indexed: 02/06/2024]
Abstract
The production of medium chain fatty acids (MCFAs) through chain elongation (CE) from organic wastes/wastewater has attracted much attention, while the effects of a common inhibitor-ammonia has not been elucidated. The mechanism of ammonia affecting CE was studied by metagenomic. The lag phase duration of caproate production was increased, and the maximum caproate production rate was decreased by 43.4 % at 4 g-N/L, as compared to 0 g-N/L. And hydrochar (HC) alleviated the inhibition of ammonia at 4 g-N/L. Metagenomic analysis indicated that ammonia induced UBA4085 sp.FDU78 as the dominant microorganism, and metabolic reconstruction revealed its potential CE ability. Furthermore, ammonia inhibited the reverse β oxidation pathway and Acetyl-CoA production pathway. The tolerance of UBA4085 sp.FDU78 to ammonia was associated with the uptake of inorganic ions, energy conservation, and synthesis of osmoprotectants. The present study provided a deep-insight on the ammonia tolerance mechanism on the CE process.
Collapse
Affiliation(s)
- Zheng Chen
- Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP(3)), Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China
| | - Zhijian Shi
- Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP(3)), Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China
| | - Yalei Zhang
- College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China; State Key Laboratory of Pollution Control and Resource Reuse, Shanghai 200092, China
| | - Yan Shi
- Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP(3)), Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China
| | - Meichen Sun
- Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP(3)), Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China
| | - Yong Cui
- Shanghai Wujiaochang Environmental Technology Co., Ltd, Shanghai 200438, China
| | - Shicheng Zhang
- Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP(3)), Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China; Shanghai Technical Service Platform for Pollution Control and Resource Utilization of Organic Wastes, Shanghai 200438, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
| | - Gang Luo
- Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP(3)), Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China; Shanghai Technical Service Platform for Pollution Control and Resource Utilization of Organic Wastes, Shanghai 200438, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China.
| |
Collapse
|
4
|
Seid N, Ochsenreither K, Neumann A. Caproate production from Enset fiber in one-pot two-step fermentation using anaerobic fungi (Neocallimastix cameroonii strain G341) and Clostridium kluyveri DSM 555. Microb Cell Fact 2023; 22:216. [PMID: 37864174 PMCID: PMC10588050 DOI: 10.1186/s12934-023-02224-w] [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: 08/10/2023] [Accepted: 10/06/2023] [Indexed: 10/22/2023] Open
Abstract
BACKGROUND Lignocellulosic biomass plays a crucial role in creating a circular bioeconomy and minimizing environmental impact. Enset biomass is a byproduct of traditional Ethiopian Enset food processing that is thrown away in huge quantities. This study aimed to produce caproate from Enset fiber using Neocallimastix cameroonii strain G341 and Clostridium kluyveri DSM 555 in one-pot two-step fermentation. RESULTS The process started by growing N. cameroonii on Enset fiber as a carbon source for 7 days. Subsequently, the fungal culture was inoculated with active C. kluyveri preculture and further incubated. The results showed that N. cameroonii grew on 0.25 g untreated Enset fiber as the sole carbon source and produced 1.16 mmol acetate, 0.51 mmol hydrogen, and 1.34 mmol formate. In addition, lactate, succinate, and ethanol were detected in small amounts, 0.17 mmol, 0.08 mmol, and 0.7 mmol, respectively. After inoculating with C. kluyveri, 0.3 mmol of caproate and 0.48 mmol of butyrate were produced, and hydrogen production also increased to 0.95 mmol compared to sole N. cameroonii fermentation. Moreover, after the culture was supplemented with 2.18 mmol of ethanol during C. kluyveri inoculation, caproate, and hydrogen production was further increased to 1.2 and 1.36 mmol, respectively, and the consumption of acetate also increased. CONCLUSION A novel microbial cell factory was developed to convert untreated lignocellulosic Enset fiber into the medium chain carboxylic acid caproate and H2 by a co-culture of the anaerobic fungi N. cameroonii and C. kluyveri. This opens a new value chain for Enset farmers, as the process requires only locally available raw materials and low-price fermenters. As the caproate production was mainly limited by the available ethanol, the addition of locally produced ethanol-containing fermentation broth ("beer") would further increase the titer.
Collapse
Affiliation(s)
- Nebyat Seid
- Electrobiotechnology, Institute of Process Engineering in Life Science 2, Karlsruhe Institute of Technology (KIT), 76131, Karlsruhe, Germany.
- School of Chemical and Bio Engineering, Addis Ababa Institute of Technology, Addis Ababa University, P.O.B: 1176, Addis Ababa, Ethiopia.
| | - Katrin Ochsenreither
- Department of Chemical and Process Engineering, Karlsruhe Institute of Technology (KIT), 76131, Karlsruhe, Germany
| | - Anke Neumann
- Electrobiotechnology, Institute of Process Engineering in Life Science 2, Karlsruhe Institute of Technology (KIT), 76131, Karlsruhe, Germany.
| |
Collapse
|
5
|
Aboudi K, Greses S, González-Fernández C. Hydraulic Retention Time as an Operational Tool for the Production of Short-Chain Carboxylates via Anaerobic Fermentation of Carbohydrate-Rich Waste. Molecules 2023; 28:6635. [PMID: 37764411 PMCID: PMC10537262 DOI: 10.3390/molecules28186635] [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: 07/24/2023] [Revised: 08/29/2023] [Accepted: 09/11/2023] [Indexed: 09/29/2023] Open
Abstract
The carboxylate platform is a sustainable and cost-effective way to valorize wastes into biochemicals that replace those of fossil origin. Short-chain fatty acids (SCFAs) are intermediates generated during anaerobic fermentation (AF) and are considered high-value-added biochemicals among carboxylates. This investigation aimed to produce SCFAs through the AF of sugar beet molasses at 25 °C and semi-continuous feeding mode in completely stirred tank reactors. A particular focus was devoted to the role of hydraulic retention time (HRT) variation in SCFAs production and distribution profile. The highest SCFAs concentration (44.1 ± 2.3 gCOD/L) was reached at the HRT of 30 days. Caproic acid accounted for 32.5-35.5% (COD-concentration basis) at the long HRTs of 20 and 30 days due to the carbon chain elongation of shorter carboxylic acids. The findings of this study proved that HRT could be used to steer the anaerobic process toward the targeted SCFAs for specific uses. Furthermore, the successful operation at low-temperature conditions (i.e., 25 °C) makes the process economically promising.
Collapse
Affiliation(s)
- Kaoutar Aboudi
- Biotechnological Processes Unit, IMDEA Energy, Avda. Ramón de la Sagra 3, 28935 Madrid, Spain
| | - Silvia Greses
- Biotechnological Processes Unit, IMDEA Energy, Avda. Ramón de la Sagra 3, 28935 Madrid, Spain
| | - Cristina González-Fernández
- Biotechnological Processes Unit, IMDEA Energy, Avda. Ramón de la Sagra 3, 28935 Madrid, Spain
- Department of Chemical Engineering and Environmental Technology, School of Industrial Engineering, University of Valladolid, Dr. Mergelina, s/n, 47002 Valladolid, Spain
- Institute of Sustainable Processes, Dr. Mergelina, s/n, 47002 Valladolid, Spain
| |
Collapse
|
6
|
Ma J, Tan L, Xie S, Feng Y, Shi Z, Ke S, He Q, Ke Q, Zhao Q. The role of hydrochloric acid pretreated activated carbon in chain elongation of D-lactate to caproate: Adsorption and facilitation. ENVIRONMENTAL RESEARCH 2023; 233:116387. [PMID: 37302743 DOI: 10.1016/j.envres.2023.116387] [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: 02/14/2023] [Revised: 06/03/2023] [Accepted: 06/09/2023] [Indexed: 06/13/2023]
Abstract
Medium chain fatty acids (MCFA) generation is attracting growing interest due to fossil fuel depletion. To promote the production of MCFA, especially caproate, hydrochloric acid pretreated activated carbon (AC) was introduced into chain elongation fermentation. In this study, the role of pretreated AC on caproate production was investigated using lactate and butyrate as electron donor and electron acceptor, respectively. The results showed that AC did not improve the chain elongation reaction at beginning but promoted the caproate production at later stage. The addition of 15 g/L AC facilitated reactor reaching the peak of caproate concentration (78.92 mM), caproate electron efficiency (63.13%), and butyrate utilization rate (51.88%). The adsorption experiment revealed a positive correlation between the adsorption capacity of pretreated AC and the concentration as well as the carbon chain length of carboxylic acids. Moreover, the adsorption of undissociated caproate by pretreated AC contributed to a mitigated toxicity towards microorganisms, thereby facilitating the production of MCFA. Microbial community analysis revealed an increasing enrichment of key functional chain elongation bacteria, including Eubacterium, Megasphaera, Caproiciproducens, and Pseudoramibacter, but a suppression on acrylate pathway microorganism Veillonella, as the dosage of pretreated AC increasing. The findings of this study demonstrated the substantial impact of the adsorption effect of acid-pretreated AC on promoting caproate production, which would aid to the development of more efficient caproate production process.
Collapse
Affiliation(s)
- Jingwei Ma
- Hunan Engineering Research Center of Water Security Technology and Application, College of Civil Engineering, Hunan University, Changsha, 410082, PR China; Key Laboratory of Building Safety and Energy Efficiency, Ministry of Education, Hunan University, Changsha, 410082, PR China
| | - Liyi Tan
- Hunan Engineering Research Center of Water Security Technology and Application, College of Civil Engineering, Hunan University, Changsha, 410082, PR China; Key Laboratory of Building Safety and Energy Efficiency, Ministry of Education, Hunan University, Changsha, 410082, PR China
| | - Shanbiao Xie
- Hunan Engineering Research Center of Water Security Technology and Application, College of Civil Engineering, Hunan University, Changsha, 410082, PR China; Key Laboratory of Building Safety and Energy Efficiency, Ministry of Education, Hunan University, Changsha, 410082, PR China
| | - Yingxin Feng
- Hunan Engineering Research Center of Water Security Technology and Application, College of Civil Engineering, Hunan University, Changsha, 410082, PR China; Key Laboratory of Building Safety and Energy Efficiency, Ministry of Education, Hunan University, Changsha, 410082, PR China
| | - Zhou Shi
- Hunan Engineering Research Center of Water Security Technology and Application, College of Civil Engineering, Hunan University, Changsha, 410082, PR China; Key Laboratory of Building Safety and Energy Efficiency, Ministry of Education, Hunan University, Changsha, 410082, PR China
| | - Shuizhou Ke
- Hunan Engineering Research Center of Water Security Technology and Application, College of Civil Engineering, Hunan University, Changsha, 410082, PR China; Key Laboratory of Building Safety and Energy Efficiency, Ministry of Education, Hunan University, Changsha, 410082, PR China
| | - Qiulai He
- Hunan Engineering Research Center of Water Security Technology and Application, College of Civil Engineering, Hunan University, Changsha, 410082, PR China; Key Laboratory of Building Safety and Energy Efficiency, Ministry of Education, Hunan University, Changsha, 410082, PR China.
| | - Qiang Ke
- National and Local Joint Engineering Research Center of Ecological Treatment Technology for Urban Water Pollution, Wenzhou University, Wenzhou, 325035, PR China.
| | - Quanbao Zhao
- CAS Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, 1799 Jimei Road, Xiamen, 361021, PR China
| |
Collapse
|
7
|
Jin Y, de Leeuw KD, Strik DPBTB. Microbial Recycling of Bioplastics via Mixed-Culture Fermentation of Hydrolyzed Polyhydroxyalkanoates into Carboxylates. MATERIALS (BASEL, SWITZERLAND) 2023; 16:2693. [PMID: 37048987 PMCID: PMC10096456 DOI: 10.3390/ma16072693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/29/2023] [Revised: 03/24/2023] [Accepted: 03/25/2023] [Indexed: 06/19/2023]
Abstract
Polyhydroxyalkanoates (PHA) polymers are emerging within biobased biodegradable plastic products. To build a circular economy, effective recycling routes should be established for these and other end-of-life bioplastics. This study presents the first steps of a potential PHA recycling route by fermenting hydrolyzed PHA-based bioplastics (Tianan ENMATTM Y1000P; PHBV (poly(3-hydroxybutyrate-co-3-hydroxyvalerate)) into carboxylates acetate and butyrate. First, three different hydrolysis pretreatment methods under acid, base, and neutral pH conditions were tested. The highest 10% (from 158.8 g COD/L to 16.3 g COD/L) of hydrolysate yield was obtained with the alkaline pretreatment. After filtration to remove the remaining solid materials, 4 g COD/L of the hydrolyzed PHA was used as the substrate with the addition of microbial nutrients for mixed culture fermentation. Due to microbial conversion, 1.71 g/L acetate and 1.20 g/L butyrate were produced. An apparent complete bioconversion from intermediates such as 3-hydroxybutyrate (3-HB) and/or crotonate into carboxylates was found. The overall yields of the combined processes were calculated as 0.07 g acetate/g PHA and 0.049 g butyrate/g PHA. These produced carboxylates can theoretically be used to reproduce PHA or serve many other applications as part of the so-called carboxylate platform.
Collapse
Affiliation(s)
- Yong Jin
- Environmental Technology, Wageningen University & Research, 6708 WG Wageningen, The Netherlands; (Y.J.); (K.D.d.L.)
| | - Kasper D. de Leeuw
- Environmental Technology, Wageningen University & Research, 6708 WG Wageningen, The Netherlands; (Y.J.); (K.D.d.L.)
- ChainCraft B.V., 1043 AP Amsterdam, The Netherlands
| | - David P. B. T. B. Strik
- Environmental Technology, Wageningen University & Research, 6708 WG Wageningen, The Netherlands; (Y.J.); (K.D.d.L.)
| |
Collapse
|
8
|
Liu C, Usman M, Ji M, Sha J, Zhou L, Yan B. Response mechanisms of anaerobic fermentative sludge to zinc oxide nanoparticles during medium-chain carboxylates production from waste activated sludge. CHEMOSPHERE 2023; 317:137879. [PMID: 36657575 DOI: 10.1016/j.chemosphere.2023.137879] [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: 09/17/2022] [Revised: 01/10/2023] [Accepted: 01/13/2023] [Indexed: 06/17/2023]
Abstract
The conversion of waste activated sludge (WAS) into medium chain carboxylates (MCCs) has attracted much attention, while investigations of the impacts of ZnO nanoparticles (NPs) on this process are sparse. The present study showed that 8 mg/g-TSS of ZnO NPs have little effects on all key steps and the activity of anaerobes, and finally leading to unchanged MCCs production. Although 30 mg/g-TSS of ZnO NPs weakly inhibited the hydrolysis, acidogenesis, and chain elongation process, WAS solubilization was enhanced, thus, the improvement was enough to offset inhibition, also resulting in an insignificant impact on overall MCCs production. However, the improvement with ZnO NPs dosages above 100 mg/g-TSS was not sufficient to offset the biological inhibition, thus inducing negative impact on overall MCCs production. The decline of EPS induced by Zn2+ and generation of excessive reactive oxygen species (ROS) were the main factors responsible for the inhibitory effects of ZnO NPs on lower activity of anaerobes. For chain elongation process, the discriminative Clostridium IV (as MCCs-forming bacteria) with a strong adaptation to ZnO NPs (300 mg/g-TSS) was observed. The present study provided a deep understanding related to the effects of ZnO NPs on the production of MCCs production from WAS and identified a zinc resistance anaerobe, which would be significant for the evaluation of influence and alleviation of inhibition induced by ZnO NPs on the carbon cycle of organic wastes.
Collapse
Affiliation(s)
- Chao Liu
- Institute of Environmental Research at Greater Bay Area, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University, Guangzhou, 510006, PR China; National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China.
| | - Muhammad Usman
- Bioproducts Science & Engineering Laboratory (BSEL), Department of Biological Systems Engineering, Washington State University (WSU), Richland, WA, USA
| | - Mengyuan Ji
- Department of Biology, University of Padua, Via U. Bassi 58/b, 35121, Padova, Italy
| | - Jun Sha
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China
| | - Li Zhou
- Institute of Environmental Research at Greater Bay Area, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University, Guangzhou, 510006, PR China.
| | - Bing Yan
- Institute of Environmental Research at Greater Bay Area, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University, Guangzhou, 510006, PR China
| |
Collapse
|
9
|
Arhin SG, Cesaro A, Di Capua F, Esposito G. Recent progress and challenges in biotechnological valorization of lignocellulosic materials: Towards sustainable biofuels and platform chemicals synthesis. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 857:159333. [PMID: 36220479 DOI: 10.1016/j.scitotenv.2022.159333] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2022] [Revised: 10/04/2022] [Accepted: 10/05/2022] [Indexed: 06/16/2023]
Abstract
Lignocellulosic materials (LCM) have garnered attention as feedstocks for second-generation biofuels and platform chemicals. With an estimated annual production of nearly 200 billion tons, LCM represent an abundant source of clean, renewable, and sustainable carbon that can be funneled to numerous biofuels and platform chemicals by sustainable microbial bioprocessing. However, the low bioavailability of LCM due to the recalcitrant nature of plant cell components, the complexity and compositional heterogeneity of LCM monomers, and the limited metabolic flexibility of wild-type product-forming microorganisms to simultaneously utilize various LCM monomers are major roadblocks. Several innovative strategies have been proposed recently to counter these issues and expedite the widespread commercialization of biorefineries using LCM as feedstocks. Herein, we critically summarize the recent advances in the biological valorization of LCM to value-added products. The review focuses on the progress achieved in the development of strategies that boost efficiency indicators such as yield and selectivity, minimize carbon losses via integrated biorefinery concepts, facilitate carbon co-metabolism and carbon-flux redirection towards targeted products using recently engineered microorganisms, and address specific product-related challenges, to provide perspectives on future research needs and developments. The strategies and views presented here could guide future studies in developing feasible and economically sustainable LCM-based biorefineries as a crucial node in achieving carbon neutrality.
Collapse
Affiliation(s)
- Samuel Gyebi Arhin
- Department of Civil, Architectural and Environmental Engineering, University of Naples Federico II, Via Claudio 21, 80125 Naples, Italy.
| | - Alessandra Cesaro
- Department of Civil, Architectural and Environmental Engineering, University of Naples Federico II, Via Claudio 21, 80125 Naples, Italy
| | - Francesco Di Capua
- School of Engineering, University of Basilicata, via dell'Ateneo Lucano 10, 85100 Potenza, Italy
| | - Giovanni Esposito
- Department of Civil, Architectural and Environmental Engineering, University of Naples Federico II, Via Claudio 21, 80125 Naples, Italy
| |
Collapse
|
10
|
Yu D, Cheng S, Cao F, Varrone C, He Z, Liu W, Yue X, Zhou A. Unveiling the bioelectrocatalyzing behaviors and microbial ecological mechanisms behind caproate production without exogenous electron donor. ENVIRONMENTAL RESEARCH 2022; 215:114077. [PMID: 35981610 DOI: 10.1016/j.envres.2022.114077] [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: 06/10/2022] [Revised: 08/04/2022] [Accepted: 08/05/2022] [Indexed: 06/15/2023]
Abstract
Bioelectrochemical systems were proposed as a promising approach for the efficient valorization of biomass into 6-8 carbon atom medium-chain fatty acids (MCFAs), the precursors for high value-added chemicals or renewable energy, via acetyl-CoA-mediated chain elongation (CE). To achieve CE processes, exogenous electron donors (EDs), e.g., ethanol or lactic acid, were normally prerequisites. This research built a microbial electrolysis cell (MEC) for MCFAs biosynthesis from acetate without exogenous EDs addition. A wide range of applied voltages (0.6-1.2 V) was first employed to investigate the bioelectrocatalyzing response. The results show that caproate and butyrate were the main products formed from acetate under different applied voltages. Maximum caproate concentration (501 ± 12 mg COD/L) was reached at 0.8 V on day 3. Under this applied voltage, hydrogen partial pressure stabilized at about 0.1 bar, beneficial for MCFA production. Electron and carbon balances revealed that the electron-accepting capacity achieved 32% at 0.8 V, showing the highest interspecies electron transfer efficiency. Most of the carbon was recovered in the form of caproate (carbon loss was 9%). MiSeq sequencing revealed Rhodobacter and Clostridium_sensu_stricto playing the crucial role in the biosynthesis of caproate, while Acetobacterium, Acetoanaerobium, and Acetobacter represented the main ED contributors. Four available flora, i.e., homo-acetogen, anaerobic fermentation bacteria, electrode active bacteria, and nitrate-reducing bacteria, interacted and promoted caproate synthesis by molecular ecological network analysis.
Collapse
Affiliation(s)
- Delin Yu
- College of Environmental Science and Engineering, Taiyuan University of Technology, Taiyuan, China
| | - Shuanglan Cheng
- College of Environmental Science and Engineering, Taiyuan University of Technology, Taiyuan, China
| | - Fang Cao
- College of Environmental Science and Engineering, Taiyuan University of Technology, Taiyuan, China
| | - Cristiano Varrone
- Department of Chemistry and BioScience, Aalborg University, Copenhagen, Denmark
| | - Zhangwei He
- Key Laboratory of Northwest Water Resource, Environment and Ecology, Ministry of Education, Xi'an University of Architecture and Technology, Xi'an, 710055, China
| | - Wenzong Liu
- School of Civil and Environmental Engineering, Harbin Institute of Technology Shenzhen, Shenzhen, 51805, China
| | - Xiuping Yue
- College of Environmental Science and Engineering, Taiyuan University of Technology, Taiyuan, China; Shanxi Engineer Research Institute of Sludge Disposition and Resources, Taiyuan University of Technology, Taiyuan, China
| | - Aijuan Zhou
- College of Environmental Science and Engineering, Taiyuan University of Technology, Taiyuan, China; Shanxi Engineer Research Institute of Sludge Disposition and Resources, Taiyuan University of Technology, Taiyuan, China.
| |
Collapse
|
11
|
Current Trends in Biological Valorization of Waste-Derived Biomass: The Critical Role of VFAs to Fuel A Biorefinery. FERMENTATION-BASEL 2022. [DOI: 10.3390/fermentation8090445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The looming climate and energy crises, exacerbated by increased waste generation, are driving research and development of sustainable resource management systems. Research suggests that organic materials, such as food waste, grass, and manure, have potential for biotransformation into a range of products, including: high-value volatile fatty acids (VFAs); various carboxylic acids; bioenergy; and bioplastics. Valorizing these organic residues would additionally reduce the increasing burden on waste management systems. Here, we review the valorization potential of various sustainably sourced feedstocks, particularly food wastes and agricultural and animal residues. Such feedstocks are often micro-organism-rich and well-suited to mixed culture fermentations. Additionally, we touch on the technologies, mainly biological systems including anaerobic digestion, that are being developed for this purpose. In particular, we provide a synthesis of VFA recovery techniques, which remain a significant technological barrier. Furthermore, we highlight a range of challenges and opportunities which will continue to drive research and discovery within the field. Analysis of the literature reveals growing interest in the development of a circular bioeconomy, built upon a biorefinery framework, which utilizes biogenic VFAs for chemical, material, and energy applications.
Collapse
|
12
|
Zhang Z, Ni BJ, Zhang L, Liu Z, Fu W, Dai X, Sun J. Medium-chain fatty acids production from carbohydrates-rich wastewater through two-stage yeast biofilm processes without external electron donor addition: Biofilm development and pH impact. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 828:154428. [PMID: 35276160 DOI: 10.1016/j.scitotenv.2022.154428] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 03/04/2022] [Accepted: 03/05/2022] [Indexed: 05/12/2023]
Abstract
The production of medium-chain fatty acids (MCFAs) is considered promising for carbon resource recovery from waste streams. However, a large quantity of external electron donors are often required, causing great cost and environmental impact. Therefore, in this study, a two-stage technology was developed to produce MCFAs from carbohydrate-rich wastewater without external electron donor addition, with the biofilm development and pH impact being explored. Stage I aimed at converting organics into ethanol and a yeast biofilm reactor is innovatively applied. The results showed that the yeast biofilm could quickly form on carriers with steady-state thickness reaching 50-200 μm. However, the attachment of yeast biofilm was weak at the initial stage so that the violent turbulence should be avoided during operation. The polyurethane foam was the most suitable for yeast biofilm development among the tested carriers, as evidenced by the highest ethanol production, accounting for 74.2% of soluble organics. The Nakaseomyces was the main fungal genus in the steady-state biofilm, while lactic acid bacteria were also developed, resulting in lactate and acetate production. In Stage II, the yeast biofilm reactor effluent was applied for MCFA production at different pH (5-8). However, the MCFA production selectivity was significantly affected by pH, with 65.2% at pH of 5 but decreasing substantially to 3.0% at pH of 8. Both the microbial and electron transfer efficiency analysis suggested that mildly acidic pH can promote the electron transfer from ethanol toward the chain elongation process instead of its excessive oxidation. Thus, if conditions of online extraction or microbial tolerance permit, a lower pH should be recommended for Stage II in the developed technology as well as other ethanol-based MCFA production process. This is a conceptual study that eliminated external electron donor addition in MCFAs production and provide a sustainable and reliable way in carbon resources recovery.
Collapse
Affiliation(s)
- Zisha Zhang
- State Key Laboratory of Pollution Control and Resource Reuse, Key Laboratory of Yangtze River Water Environment, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
| | - Bing-Jie Ni
- Centre for Technology in Water and Wastewater (CTWW), School of Civil and Environmental Engineering, University of Technology Sydney (UTS), Sydney, NSW 2007, Australia
| | - Lu Zhang
- State Key Laboratory of Pollution Control and Resource Reuse, Key Laboratory of Yangtze River Water Environment, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
| | - Zhitong Liu
- State Key Laboratory of Pollution Control and Resource Reuse, Key Laboratory of Yangtze River Water Environment, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
| | - Weng Fu
- School of Chemical Engineering, The University of Queensland, St. Lucia, QLD 4072, Australia
| | - Xiaohu Dai
- State Key Laboratory of Pollution Control and Resource Reuse, Key Laboratory of Yangtze River Water Environment, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
| | - Jing Sun
- State Key Laboratory of Pollution Control and Resource Reuse, Key Laboratory of Yangtze River Water Environment, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China; Anhui Provincial Key Laboratory of Environmental Pollution Control and Resource Reuse, Hefei 230000, China.
| |
Collapse
|
13
|
Tang J, Dai K, Wang QT, Zheng SJ, Hong SD, Jianxiong Zeng R, Zhang F. Caproate production from xylose via the fatty acid biosynthesis pathway by genus Caproiciproducens dominated mixed culture fermentation. BIORESOURCE TECHNOLOGY 2022; 351:126978. [PMID: 35276377 DOI: 10.1016/j.biortech.2022.126978] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 03/05/2022] [Accepted: 03/07/2022] [Indexed: 06/14/2023]
Abstract
Caproate production from organic wastes is deemed as a novel strategy in mixed culture fermtation (MCF). However, producing caproate from natural sugar of xylose by MCF is seldom reported and the metabolic pathway is still unclear. Thus, the caproate production from xylose was investigated in this study by mesophilic MCF. The results showed that the caproate concentration from xylose (10 g/L) was 1.2 ± 0.17 g/L (equal to 2.7 gCOD/L) under pH 5.0. Dosing extra ethanol of 5 g/L could slightly increase the caproate production by ∼ 30% (i.e., 1.6 g/L). While dosing extra acetate of 5 g/L negatively affected the caproate production, which was just 0.2 g/L. The microbial analysis illustrated that genus Caproiciproducens was a main identified caproate producer, occupying over 80% of enriched mixed culture. The fatty acid biosynthesis pathway was identified via metagenomic analysis. These unexpected differences extended the understanding of caproate production from organic wastes.
Collapse
Affiliation(s)
- Jie Tang
- Center of Wastewater Resource Recovery, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Kun Dai
- Center of Wastewater Resource Recovery, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Qing-Ting Wang
- Center of Wastewater Resource Recovery, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Si-Jie Zheng
- Center of Wastewater Resource Recovery, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Si-Di Hong
- Center of Wastewater Resource Recovery, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Raymond Jianxiong Zeng
- Center of Wastewater Resource Recovery, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Fang Zhang
- Center of Wastewater Resource Recovery, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China.
| |
Collapse
|
14
|
Contreras-Dávila CA, Zuidema N, Buisman CJN, Strik DPBTB. Reactor microbiome enriches vegetable oil with n-caproate and n-caprylate for potential functionalized feed additive production via extractive lactate-based chain elongation. BIOTECHNOLOGY FOR BIOFUELS 2021; 14:232. [PMID: 34872602 PMCID: PMC8647473 DOI: 10.1186/s13068-021-02084-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 11/21/2021] [Indexed: 06/13/2023]
Abstract
BACKGROUND Biotechnological processes for efficient resource recovery from residual materials rely on complex conversions carried out by reactor microbiomes. Chain elongation microbiomes produce valuable medium-chain carboxylates (MCC) that can be used as biobased starting materials in the chemical, agriculture and food industry. In this study, sunflower oil is used as an application-compatible solvent to accumulate microbially produced MCC during extractive lactate-based chain elongation. The MCC-enriched solvent is harvested as a potential novel product for direct application without further MCC purification, e.g., direct use for animal nutrition. Sunflower oil biocompatibility, in situ extraction performance and effects on chain elongation were evaluated in batch and continuous experiments. Microbial community composition and dynamics of continuous experiments were analyzed based on 16S rRNA gene sequencing data. Potential applications of MCC-enriched solvents along with future research directions are discussed. RESULTS Sunflower oil showed high MCC extraction specificity and similar biocompatibility to oleyl alcohol in batch extractive fermentation of lactate and food waste. Continuous chain elongation microbiomes produced the MCC n-caproate (nC6) and n-caprylate (nC8) from L-lactate and acetate at pH 5.0 standing high undissociated n-caproic acid concentrations (3 g L-1). Extractive chain elongation with sunflower oil relieved apparent toxicity of MCC and production rates and selectivities reached maximum values of 5.16 ± 0.41 g nC6 L-1 d-1 (MCC: 11.5 g COD L-1 d-1) and 84 ± 5% (e- eq MCC per e- eq products), respectively. MCC were selectively enriched in sunflower oil to concentrations up to 72 g nC6 L-1 and 3 g nC8 L-1, equivalent to 8.3 wt% in MCC-enriched sunflower oil. Fermentation at pH 7.0 produced propionate and n-butyrate instead of MCC. Sunflower oil showed stable linoleic and oleic acids composition during extractive chain elongation regardless of pH conditions. Reactor microbiomes showed reduced diversity at pH 5.0 with MCC production linked to Caproiciproducens co-occurring with Clostridium tyrobutyricum, Clostridium luticellarii and Lactobacillus species. Abundant taxa at pH 7.0 were Anaerotignum, Lachnospiraceae and Sporoanaerobacter. CONCLUSIONS Sunflower oil is a suitable biobased solvent to selectively concentrate MCC. Extractive reactor microbiomes produced MCC with improved selectivity and production rate, while downstream processing complexity was reduced. Potential applications of MCC-enriched solvents may include feed, food and biofuels purposes.
Collapse
Affiliation(s)
- Carlos A. Contreras-Dávila
- Environmental Technology, Wageningen University & Research, Bornse Weilanden 9, 6708 WG Wageningen, The Netherlands
| | - Norwin Zuidema
- Environmental Technology, Wageningen University & Research, Bornse Weilanden 9, 6708 WG Wageningen, The Netherlands
| | - Cees J. N. Buisman
- Environmental Technology, Wageningen University & Research, Bornse Weilanden 9, 6708 WG Wageningen, The Netherlands
| | - David P. B. T. B. Strik
- Environmental Technology, Wageningen University & Research, Bornse Weilanden 9, 6708 WG Wageningen, The Netherlands
| |
Collapse
|
15
|
Wang J, Yin Y. Biological production of medium-chain carboxylates through chain elongation: An overview. Biotechnol Adv 2021; 55:107882. [PMID: 34871718 DOI: 10.1016/j.biotechadv.2021.107882] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 11/01/2021] [Accepted: 11/28/2021] [Indexed: 12/15/2022]
Abstract
Medium chain carboxylates (MCCs) have wide applications in various industries, but the traditional MCCs production methods are costly and unsustainable. Anaerobic fermentation offers a more scalable, economical and eco-friendly platform for producing MCCs through chain elongation which converts short chain carboxylates and electron donor into more valuable MCCs. However, the underlying microbial pathways are not well understood. In this review, biological production of MCCs through chain elongation is introduced elaborately, including the metabolic pathways, electron donor and substrates, microorganisms and influencing factors. Then, the strategies for enhancing MCCs production are extensively analyzed and summarized, along with the technologies for MCCs separation from the fermentation broth. Finally, challenges and perspectives concerning the large-scale MCCs production are proposed, providing suggestions for the future research. Extensive review demonstrated that anaerobic fermentation has great potential in achieving economical and sustainable MCCs production from complex organic substrates, including organic waste streams, which would significantly broaden the application of MCCs, especially in the renewable energy field. An interdisciplinary approach with knowledge from microbiology and biochemistry to chemical separations and environmental engineering is required to use this promising technology as a valorization method for converting organic biomass or organic wastes into valuable MCCs.
Collapse
Affiliation(s)
- Jianlong Wang
- Laboratory of Environmental Technology, INET, Tsinghua University, Beijing 100084, PR China; Beijing Key Laboratory of Radioactive Waste Treatment, Tsinghua University, Beijing 100084, PR China.
| | - Yanan Yin
- Laboratory of Environmental Technology, INET, Tsinghua University, Beijing 100084, PR China
| |
Collapse
|
16
|
Lu S, Jin H, Wang Y, Tao Y. Genome-Wide Transcriptomic Analysis of n-Caproic Acid Production in Ruminococcaceae Bacterium CPB6 with Lactate Supplementation. J Microbiol Biotechnol 2021; 31:1533-1544. [PMID: 34489376 PMCID: PMC9705837 DOI: 10.4014/jmb.2107.07009] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Revised: 08/25/2021] [Accepted: 08/25/2021] [Indexed: 12/15/2022]
Abstract
n-Caproic acid (CA) is gaining increased attention due to its high value as a chemical feedstock. Ruminococcaceae bacterium strain CPB6 is an anaerobic mesophilic bacterium that is highly prolific in its ability to perform chain elongation of lactate to CA. However, little is known about the genome-wide transcriptional analysis of strain CPB6 for CA production triggered by the supplementation of exogenous lactate. In this study, cultivation of strain CPB6 was carried out in the absence and presence of lactate. Transcriptional profiles were analyzed using RNA-seq, and differentially expressed genes (DEGs) between the lactate-supplemented cells and control cells without lactate were analyzed. The results showed that lactate supplementation led to earlier CA p,roduction, and higher final CA titer and productivity. 295 genes were substrate and/or growth dependent, and these genes cover crucial functional categories. Specifically, 5 genes responsible for the reverse β-oxidation pathway, 11 genes encoding ATP-binding cassette (ABC) transporters, 6 genes encoding substrate-binding protein (SBP), and 4 genes encoding phosphotransferase system (PTS) transporters were strikingly upregulated in response to the addition of lactate. These genes would be candidates for future studies aiming at understanding the regulatory mechanism of lactate conversion into CA, as well as for the improvement of CA production in strain CPB6. The findings presented herein reveal unique insights into the biomolecular effect of lactate on CA production at the transcriptional level.
Collapse
Affiliation(s)
- Shaowen Lu
- CAS Key Laboratory of Environmental and Applied Microbiology and Environmental Microbiology Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, P.R. China
| | - Hong Jin
- School of Basic Medical Science, Chengdu Medical College, Chengdu 610083, P.R. China
| | - Yi Wang
- Department of Biosystems Engineering, Auburn University, Auburn, Alabama, Alabama 36849, USA
| | - Yong Tao
- CAS Key Laboratory of Environmental and Applied Microbiology and Environmental Microbiology Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, P.R. China,Faculty of Bioengineering, Sichuan University of Science and Engineering, Xueyuan Street 180#, Huixing Rd. Zigong 643000, P.R. China,Corresponding author Phone: 86-028-82890211 Fax: 86-028-82890211 E-mail:
| |
Collapse
|
17
|
de Leeuw KD, Ahrens T, Buisman CJN, Strik DPBTB. Open Culture Ethanol-Based Chain Elongation to Form Medium Chain Branched Carboxylates and Alcohols. Front Bioeng Biotechnol 2021; 9:697439. [PMID: 34485254 PMCID: PMC8416115 DOI: 10.3389/fbioe.2021.697439] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Accepted: 07/30/2021] [Indexed: 11/18/2022] Open
Abstract
Chain elongation fermentation allows for the synthesis of biobased chemicals from complex organic residue streams. To expand the product spectrum of chain elongation technology and its application range we investigated 1) how to increase selectivity towards branched chain elongation and 2) whether alternative branched carboxylates such as branched valerates can be used as electron acceptors. Elongation of isobutyrate elongation towards 4-methyl-pentanoate was achieved with a selectivity of 27% (of total products, based on carbon atoms) in a continuous system that operated under CO2 and acetate limited conditions. Increasing the CO2 load led to more in situ acetate formation that increased overall chain elongation rate but decreased the selectivity of branched chain elongation. A part of this acetate formation was related to direct ethanol oxidation that seemed to be thermodynamically coupled to hydrogenotrophic carboxylate reduction to corresponding alcohols. Several alcohols including isobutanol and n-hexanol were formed. The microbiome from the continuous reactor was also able to form small amounts of 5-methyl-hexanoate likely from 3-methyl-butanoate and ethanol as substrate in batch experiments. The highest achieved concentration of isoheptanoate was 6.4 ± 0.9 mM Carbon, or 118 ± 17 mg/L, which contributed for 7% to the total amount of products (based on carbon atoms). The formation of isoheptanoate was dependent on the isoform of branched valerate. With 3-methyl-butanoate as substrate 5-methylhexanoate was formed, whereas a racemic mixture of L/D 2-methyl-butanoate did not lead to an elongated product. When isobutyrate and isovalerate were added simultaneously as substrates there was a large preference for elongation of isobutyrate over isovalerate. Overall, this work showed that chain elongation microbiomes can be further adapted with supplement of branched-electron acceptors towards the formation of iso-caproate and iso-heptanoate as well as that longer chain alcohol formation can be stimulated.
Collapse
Affiliation(s)
- Kasper D de Leeuw
- Environmental Technology, Wageningen University & Research, Wageningen, Netherlands
| | - Theresa Ahrens
- Environmental Technology, Wageningen University & Research, Wageningen, Netherlands
| | - Cees J N Buisman
- Environmental Technology, Wageningen University & Research, Wageningen, Netherlands
| | - David P B T B Strik
- Environmental Technology, Wageningen University & Research, Wageningen, Netherlands
| |
Collapse
|
18
|
Allaart MT, Stouten GR, Sousa DZ, Kleerebezem R. Product Inhibition and pH Affect Stoichiometry and Kinetics of Chain Elongating Microbial Communities in Sequencing Batch Bioreactors. Front Bioeng Biotechnol 2021; 9:693030. [PMID: 34235138 PMCID: PMC8256265 DOI: 10.3389/fbioe.2021.693030] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Accepted: 05/25/2021] [Indexed: 11/13/2022] Open
Abstract
Anaerobic microbial communities can produce carboxylic acids of medium chain length (e.g., caproate, caprylate) by elongating short chain fatty acids through reversed β-oxidation. Ethanol is a common electron donor for this process. The influence of environmental conditions on the stoichiometry and kinetics of ethanol-based chain elongation remains elusive. Here, a sequencing batch bioreactor setup with high-resolution off-gas measurements was used to identify the physiological characteristics of chain elongating microbial communities enriched on acetate and ethanol at pH 7.0 ± 0.2 and 5.5 ± 0.2. Operation at both pH-values led to the development of communities that were highly enriched (>50%, based on 16S rRNA gene amplicon sequencing) in Clostridium kluyveri related species. At both pH-values, stably performing cultures were characterized by incomplete substrate conversion and decreasing biomass-specific hydrogen production rates during an operational cycle. The process stoichiometries obtained at both pH-values were different: at pH 7.0, 71 ± 6% of the consumed electrons were converted to caproate, compared to only 30 ± 5% at pH 5.5. Operating at pH 5.5 led to a decrease in the biomass yield, but a significant increase in the biomass-specific substrate uptake rate, suggesting that the organisms employ catabolic overcapacity to deal with energy losses associated to product inhibition. These results highlight that chain elongating conversions rely on a delicate balance between substrate uptake- and product inhibition kinetics.
Collapse
Affiliation(s)
| | | | - Diana Z Sousa
- Laboratory of Microbiology, Wageningen University & Research, Wageningen, Netherlands
| | - Robbert Kleerebezem
- Department of Biotechnology, Delft University of Technology, Delft, Netherlands
| |
Collapse
|
19
|
Cabau-Peinado O, Straathof AJJ, Jourdin L. A General Model for Biofilm-Driven Microbial Electrosynthesis of Carboxylates From CO 2. Front Microbiol 2021; 12:669218. [PMID: 34149654 PMCID: PMC8211901 DOI: 10.3389/fmicb.2021.669218] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Accepted: 05/10/2021] [Indexed: 11/13/2022] Open
Abstract
Up to now, computational modeling of microbial electrosynthesis (MES) has been underexplored, but is necessary to achieve breakthrough understanding of the process-limiting steps. Here, a general framework for modeling microbial kinetics in a MES reactor is presented. A thermodynamic approach is used to link microbial metabolism to the electrochemical reduction of an intracellular mediator, allowing to predict cellular growth and current consumption. The model accounts for CO2 reduction to acetate, and further elongation to n-butyrate and n-caproate. Simulation results were compared with experimental data obtained from different sources and proved the model is able to successfully describe microbial kinetics (growth, chain elongation, and product inhibition) and reactor performance (current density, organics titer). The capacity of the model to simulate different system configurations is also shown. Model results suggest CO2 dissolved concentration might be limiting existing MES systems, and highlight the importance of the delivery method utilized to supply it. Simulation results also indicate that for biofilm-driven reactors, continuous mode significantly enhances microbial growth and might allow denser biofilms to be formed and higher current densities to be achieved.
Collapse
Affiliation(s)
- Oriol Cabau-Peinado
- Department of Biotechnology, Faculty of Applied Sciences, Delft University of Technology, Delft, Netherlands
| | - Adrie J J Straathof
- Department of Biotechnology, Faculty of Applied Sciences, Delft University of Technology, Delft, Netherlands
| | - Ludovic Jourdin
- Department of Biotechnology, Faculty of Applied Sciences, Delft University of Technology, Delft, Netherlands
| |
Collapse
|
20
|
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.
Collapse
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.
| |
Collapse
|
21
|
Fermentation of Organic Residues to Beneficial Chemicals: A Review of Medium-Chain Fatty Acid Production. Processes (Basel) 2020. [DOI: 10.3390/pr8121571] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Medium-chain fatty acids (MCFAs) have a variety of uses in the production of industrial chemicals, food, and personal care products. These compounds are often produced through palm refining, but recent work has demonstrated that MCFAs can also be produced through the fermentation of complex organic substrates, including organic waste streams. While “chain elongation” offers a renewable platform for producing MCFAs, there are several limitations that need to be addressed before full-scale implementation becomes widespread. Here, we review the history of work on MCFA production by both pure and mixed cultures of fermenting organisms, and the unique metabolic features that lead to MCFA production. We also offer approaches to address the remaining challenges and increase MCFA production from renewable feedstocks.
Collapse
|
22
|
Candry P, Radić L, Favere J, Carvajal-Arroyo JM, Rabaey K, Ganigué R. Mildly acidic pH selects for chain elongation to caproic acid over alternative pathways during lactic acid fermentation. WATER RESEARCH 2020; 186:116396. [PMID: 32920334 DOI: 10.1016/j.watres.2020.116396] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 08/28/2020] [Accepted: 09/05/2020] [Indexed: 06/11/2023]
Abstract
Carbohydrate-rich waste streams can be used for bioproduction of medium-chain carboxylic acids (MCCA) such as caproic acid. The carbohydrates in these streams can be converted to lactic acid as the initial fermentation product, which can then be fermented to MCCA by chain elongation. In this process, chain elongators compete for lactic acid with other bacterial groups that, for instance, ferment lactic acid to propionic and acetic acid. Understanding the drivers that control the competition between these two pathways is essential to maximizing MCCA production. This study aimed to investigate the competition between chain elongating and propionic acid producing organisms as a function of operational pH. Operation of long-term lactic acid fermenting reactors with varying pH values showed that pH values above 6 resulted in a propionic acid producing community dominated by Veillonella and Aminobacterium. At pH values below 6, the community moved towards chain elongation, with communities dominated by Caproiciproducens. Short-term incubations showed that rates of lactic acid consumption were strongly reduced at pH below 6 (7.7 ± 1.2 mM lactic acid·h-1 at pH 6.5; 0.74 ± 0.33 mM lactic acid·h-1 at pH 5.5). Similar to observations in long-term reactors, when a chain elongating community adapted to pH 5.5 was used for short-term incubations at pH 6.5, propionic acid was the dominant product. The results of this study show that pH below 6 stimulate lactic acid chain elongators through kinetic effects, and potentially improved energetics, providing a tool for microbial management of MCCA-producing systems.
Collapse
Affiliation(s)
- Pieter Candry
- Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, 9000 Ghent, Belgium
| | - Ljubomir Radić
- Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, 9000 Ghent, Belgium
| | - Jorien Favere
- Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, 9000 Ghent, Belgium
| | - Jose Maria Carvajal-Arroyo
- Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, 9000 Ghent, Belgium
| | - Korneel Rabaey
- Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, 9000 Ghent, Belgium; CAPTURE (www.capture-resources.be), Coupure Links 653, 9000 Ghent, Belgium
| | - Ramon Ganigué
- Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, 9000 Ghent, Belgium; CAPTURE (www.capture-resources.be), Coupure Links 653, 9000 Ghent, Belgium.
| |
Collapse
|
23
|
Pan XR, Huang L, Fu XZ, Yuan YR, Liu HQ, Li WW, Yu L, Zhao QB, Zuo J, Chen L, Lam PKS. Long-term, selective production of caproate in an anaerobic membrane bioreactor. BIORESOURCE TECHNOLOGY 2020; 302:122865. [PMID: 32004814 DOI: 10.1016/j.biortech.2020.122865] [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: 12/06/2019] [Revised: 01/16/2020] [Accepted: 01/21/2020] [Indexed: 06/10/2023]
Abstract
Fermentative caproate production from wastewater is attractive but is currently limited by the low product purity and concentration. In this work, continuous, selective production of caproate from acetate and ethanol, the common products of wastewater anaerobic fermentation, was achieved in an anaerobic membrane bioreactor (AnMBR). The reactor was continuously operated for over 522 days without need for chemical cleaning. With an ethanol-to-acetate ratio of 3.0, the effluent caproate concentration was 2.62 g/L on average and the caproate ratio in liquid products reached 74%. Further raising the influent ethanol content slightly increased the effluent caproate level but lowered the product selectivity and resulted in microbial inhibition. The Clostridia (the major caproate-producing bacteria) and Methanobacterium species (which consume hydrogen to alleviate microbial inhibition) was significantly enriched in the acclimated sludge. Our results imply a great potential of utilizing AnMBR to recover caproate from the effluent of wastewater acidogenic fermentation process.
Collapse
Affiliation(s)
- Xin-Rong Pan
- CAS Key Laboratory of Urban Pollutant Conversion, Department of Chemistry, University of Science and Technology of China, Hefei 230026, China; Department of Chemistry, City University of Hong Kong, Hong Kong SAR 999077, China; State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China
| | - Liang Huang
- CAS Key Laboratory of Urban Pollutant Conversion, Department of Chemistry, University of Science and Technology of China, Hefei 230026, China
| | - Xian-Zhong Fu
- CAS Key Laboratory of Urban Pollutant Conversion, Department of Chemistry, University of Science and Technology of China, Hefei 230026, China
| | - Yan-Ru Yuan
- CAS Key Laboratory of Urban Pollutant Conversion, Department of Chemistry, University of Science and Technology of China, Hefei 230026, China
| | - Hou-Qi Liu
- CAS Key Laboratory of Urban Pollutant Conversion, Department of Chemistry, University of Science and Technology of China, Hefei 230026, China
| | - Wen-Wei Li
- CAS Key Laboratory of Urban Pollutant Conversion, Department of Chemistry, University of Science and Technology of China, Hefei 230026, China.
| | - Lei Yu
- Department of Environmental Engineering, Nanjing Forestry University, Nanjing 210037, China
| | - Quan-Bao Zhao
- CAS Key Laboratory of Urban Pollutant Conversion, Department of Chemistry, University of Science and Technology of China, Hefei 230026, China
| | - Jiane Zuo
- State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China
| | - Lei Chen
- State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China
| | - Paul Kwan-Sing Lam
- Department of Chemistry, City University of Hong Kong, Hong Kong SAR 999077, China
| |
Collapse
|
24
|
San-Valero P, Abubackar HN, Veiga MC, Kennes C. Effect of pH, yeast extract and inorganic carbon on chain elongation for hexanoic acid production. BIORESOURCE TECHNOLOGY 2020; 300:122659. [PMID: 31893537 DOI: 10.1016/j.biortech.2019.122659] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Revised: 12/17/2019] [Accepted: 12/18/2019] [Indexed: 06/10/2023]
Abstract
Several anaerobic bioconversion technologies produce short chain volatile fatty acids and sometimes ethanol, which can together be elongated to hexanoic acid (C6 acid) by Clostridium kluyveri in a secondary fermentation process. Initiatives are needed to further optimize the process. Therefore, five strategies were tested aiming at elucidating their influence on hexanoic acid production from mixtures of acetic acid, butyric acid and ethanol. pH-regulated bioreactors, maintained at pH 7.5, 6.8 or 6.4 led to maximum C6 acid concentrations of, respectively, 19.4, 18.3 and 13.3 g L-1. At pH 6.8, yeast extract omission resulted in a decrease of the hexanoic acid concentration to 12.0 g L-1 while the addition of an inorganic carbon source, such as bicarbonate, for pH control, increased the C6 acid concentration up to 21.4 g L-1. This research provides guidelines for efficient improved production of hexanoic acid by pure cultures of C. kluyveri, contributing to the state of art.
Collapse
Affiliation(s)
- Pau San-Valero
- Chemical Engineering Laboratory, Faculty of Sciences and Center for Advanced Scientific Research (CICA), University of La Coruña, Rúa da Fraga 10, E - 15008 La Coruña, Spain
| | - Haris Nalakath Abubackar
- Chemical Engineering Laboratory, Faculty of Sciences and Center for Advanced Scientific Research (CICA), University of La Coruña, Rúa da Fraga 10, E - 15008 La Coruña, Spain
| | - María C Veiga
- Chemical Engineering Laboratory, Faculty of Sciences and Center for Advanced Scientific Research (CICA), University of La Coruña, Rúa da Fraga 10, E - 15008 La Coruña, Spain
| | - Christian Kennes
- Chemical Engineering Laboratory, Faculty of Sciences and Center for Advanced Scientific Research (CICA), University of La Coruña, Rúa da Fraga 10, E - 15008 La Coruña, Spain.
| |
Collapse
|
25
|
Zhang W, Zhang F, Li YX, Jiang Y, Zeng RJ. No difference in inhibition among free acids of acetate, propionate and butyrate on hydrogenotrophic methanogen of Methanobacterium formicicum. BIORESOURCE TECHNOLOGY 2019; 294:122237. [PMID: 31683454 DOI: 10.1016/j.biortech.2019.122237] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Revised: 09/25/2019] [Accepted: 10/01/2019] [Indexed: 06/10/2023]
Abstract
Free volatile fatty acids such as free acetic acid (FAA) and free butyrate acid (FBA) are true inhibitors of hydrogenotrophic methanogens (HM) in mixed culture. However, their inhibitory effects on pure culture of HM remain unclear. In this study, a typical HM of Methanobacterium formicicum demonstrated no difference in toxicity conferred by FAA, free propionate acid (FPA), or FBA in regard to the specific methanogenic activity (SMA) based on the C50% (0.19, 0.17, and 0.23 g/L, respectively) and recoverable concentration values (0.97, 0.69, and 0.61 g/L, respectively). These results were within the same order of magnitude. The concentrations of FAA, FBA, and FPA all correlated well with the SMA values according to the inhibition model. Additionally, changes in the activity of the electron transport system also agreed well with the trend in the SMA variation. Together, the results of this study provide a benchmark to control methanogenesis during industrial applications.
Collapse
Affiliation(s)
- Wei Zhang
- Centre of Wastewater Resource Recovery, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China; CAS Key Laboratory for Urban Pollutant Conversion, Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Fang Zhang
- Centre of Wastewater Resource Recovery, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Yong-Xin Li
- Centre of Wastewater Resource Recovery, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Yong Jiang
- Centre of Wastewater Resource Recovery, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Raymond Jianxiong Zeng
- Centre of Wastewater Resource Recovery, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China; CAS Key Laboratory for Urban Pollutant Conversion, Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, China.
| |
Collapse
|
26
|
Syngas-aided anaerobic fermentation for medium-chain carboxylate and alcohol production: the case for microbial communities. Appl Microbiol Biotechnol 2019; 103:8689-8709. [PMID: 31612269 DOI: 10.1007/s00253-019-10086-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 08/06/2019] [Accepted: 08/07/2019] [Indexed: 01/01/2023]
Abstract
Syngas fermentation has been successfully implemented in commercial-scale plants and can enable the biochemical conversion of the driest fractions of biomass through synthesis gas (H2, CO2, and CO). The process relies on optimized acetogenic strains able to reach and maintain high productivity of ethanol and acetate. In parallel, microbial communities have shown to be the best choice for the production of valuable medium-chain carboxylates through anaerobic fermentation of biomass, demanding low technical complexity and being able to realize simultaneous hydrolysis of the substrate. Each of the two technologies benefits from different strong points and has different challenges to overcome. This review discusses the rationales for merging these two seemingly disparate technologies by analyzing previous studies and drawing opinions based on the lessons learned from such studies. For keeping the technical demands of the resulting process low, a case is built for using microbial communities instead of pure strains. For that to occur, a shift from conventional syngas-based to "syngas-aided" anaerobic fermentation is suggested. Strategies for tackling the intricacies of working simultaneously with communities and syngas, such as competing pathways, and thermodynamic aspects are discussed as well as the stoichiometry and economic feasibility of the concept. Overall, syngas-aided anaerobic fermentation seems to be a promising concept for the biorefinery of the future. However, the effects of process parameters on microbial interactions have to be understood in greater detail, in order to achieve and sustain feasible medium-chain carboxylate and alcohol productivity.
Collapse
|
27
|
Enhanced Anaerobic Mixed Culture Fermentation with Anion-Exchange Resin for Caproate Production. Processes (Basel) 2019. [DOI: 10.3390/pr7070404] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The bioproduction of caproate from organic waste by anaerobic mixed culture is a very attractive technology for upgrading low-grade biomass to a high-value resource. However, the caproate production process is markedly restricted by the feedback inhibition of caproate. In this study, four types of anion-exchange resin were investigated for their enhancing capability in caproate fermentation of anaerobic mixed culture. The strong base anion-exchange resin D201 showed the highest adsorption capacity (62 mg/g), selectivity (7.50), and desorption efficiency (88.2%) for caproate among the test resins. Subsequently, the optimal desorption temperature and NaOH concentration of eluent for D201 were determined. The adsorption and desorption efficiency of D201 remained stable during eight rounds of the adsorption–desorption cycle, indicating a satisfactory reusability of D201. Finally, performances of caproate fermentation with and without resin adsorption for carboxylate were evaluated. The results demonstrated that the final concentration of caproate was improved from 12.43 ± 0.29 g/L (without adsorption) to 17.30 ± 0.13 g/L (with adsorption) and the maximum caproate production rate was improved from 0.60 ± 0.01 g/L/d to 2.03 ± 0.02 g/L/d. In the group with adsorption, the cumulative caproate production was increased to 29.10 ± 0.33 g/L broth, which was 134% higher than that of the control group. Therefore, this study provides effective approaches to enhance caproate production.
Collapse
|
28
|
Yu J, Huang Z, Wu P, Zhao M, Miao H, Liu C, Ruan W. Performance and microbial characterization of two-stage caproate fermentation from fruit and vegetable waste via anaerobic microbial consortia. BIORESOURCE TECHNOLOGY 2019; 284:398-405. [PMID: 30959377 DOI: 10.1016/j.biortech.2019.03.124] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Revised: 03/24/2019] [Accepted: 03/25/2019] [Indexed: 05/24/2023]
Abstract
The regulation of two-stage caproate fermentation from fruit and vegetable waste (FVW) via anaerobic microbial consortia was investigated in this study. The results showed the highest caproate production achieved 14.9 g/L at the optimal inoculum to substrate ratio (ISR) of 2:1, ethanol to acid ratio (E/A) of 4:1, and pH of 7.5. The caproate yield and selectivity respectively reached 0.62 g/g and 80.8% (as COD). In acidification stage, an appropriate ISR provided a high conversion efficiency and more acetate formation, which was beneficial to caproate biosynthesis. In caproate production stage, chain elongation performance was sensitive to E/A and pH condition. Butyrate became the main by-product at low E/A or acidic conditions, while excessive ethanol or alkaline condition seriously suppressed substrate conversion. The caproate fermentation was dominated by Clostridium kluyveri. Furthermore, caproate formation was uncoupled with Clostridium kluyveri proliferation, which was mainly generated during the middle and late stages of growth.
Collapse
Affiliation(s)
- Jiangnan Yu
- Jiangsu Key Laboratory of Anaerobic Biotechnology, School of Environment and Civil Engineering, Jiangnan University, Wuxi 214122, China
| | - Zhenxing Huang
- Jiangsu Key Laboratory of Anaerobic Biotechnology, School of Environment and Civil Engineering, Jiangnan University, Wuxi 214122, China; Jiangsu Collaborative Innovation Center of Technology and Material of Water Treatment, Suzhou 215011, China
| | - Peng Wu
- School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou 215009, China
| | - Mingxing Zhao
- Jiangsu Key Laboratory of Anaerobic Biotechnology, School of Environment and Civil Engineering, Jiangnan University, Wuxi 214122, China
| | - Hengfeng Miao
- Jiangsu Key Laboratory of Anaerobic Biotechnology, School of Environment and Civil Engineering, Jiangnan University, Wuxi 214122, China; Jiangsu Engineering Laboratory for Biomass Energy and Carbon Reduction Technology, Jiangnan University, Wuxi 214122, China
| | - Chunmei Liu
- Jiangsu Key Laboratory of Anaerobic Biotechnology, School of Environment and Civil Engineering, Jiangnan University, Wuxi 214122, China
| | - Wenquan Ruan
- Jiangsu Key Laboratory of Anaerobic Biotechnology, School of Environment and Civil Engineering, Jiangnan University, Wuxi 214122, China; Jiangsu Collaborative Innovation Center of Technology and Material of Water Treatment, Suzhou 215011, China.
| |
Collapse
|
29
|
Zhang C, Yang L, Tsapekos P, Zhang Y, Angelidaki I. Immobilization of Clostridium kluyveri on wheat straw to alleviate ammonia inhibition during chain elongation for n-caproate production. ENVIRONMENT INTERNATIONAL 2019; 127:134-141. [PMID: 30913458 DOI: 10.1016/j.envint.2019.03.032] [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: 10/11/2018] [Revised: 02/18/2019] [Accepted: 03/14/2019] [Indexed: 06/09/2023]
Abstract
Biosynthesis of n-caproate from waste streams rich in acetate and ethanol through chain elongation has offered a potentially sustainable way for future production of liquid biofuels. However, most of the waste streams that fit with the purpose (e.g., digestate) are also rich in ammonium which at high concentration may cause toxic effects on the bioconversion process. This study aims to develop a robust, efficient, and cost-effective chain elongation process with high caproate productivity and tolerance to high ammonia concentration, through immobilization of Clostridium kluyveri on biomass particles as immobilization material. The threshold ammonia concentration for suspended cells cultivation was 2.1 g/L, while it was higher than 5.0 g/L for the wheat straw immobilized system. The caproate production process was dependent on the selected carriers and was performing in the order of: wheat straw > grass straw > saw dust. The biofilm immobilized on the wheat straw showed good reuse capability for caproate production under high ammonia concentration. Moreover, the lag phase for caproate production was shortened from 72 to 30 h after 8 times reuse. These results proved that caproate production and tolerance of chain elongation to ammonia toxicity could be enhanced via cell immobilization. This study offers insight into future development of efficient and cost-effective chain elongation system for production of caproate and other value-added products.
Collapse
Affiliation(s)
- Cunsheng Zhang
- School of Food and Biological Engineering, Jiangsu University, Zhenjiang 212013, PR China
| | - Li Yang
- School of Food and Biological Engineering, Jiangsu University, Zhenjiang 212013, PR China
| | - Panagiotis Tsapekos
- Department of Environmental Engineering, Technical University of Denmark, DK-2800 Lyngby, Denmark
| | - Yifeng Zhang
- Department of Environmental Engineering, Technical University of Denmark, DK-2800 Lyngby, Denmark.
| | - Irini Angelidaki
- Department of Environmental Engineering, Technical University of Denmark, DK-2800 Lyngby, Denmark
| |
Collapse
|
30
|
De Groof V, Coma M, Arnot T, Leak DJ, Lanham AB. Medium Chain Carboxylic Acids from Complex Organic Feedstocks by Mixed Culture Fermentation. Molecules 2019; 24:E398. [PMID: 30678297 PMCID: PMC6384945 DOI: 10.3390/molecules24030398] [Citation(s) in RCA: 71] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 01/10/2019] [Accepted: 01/18/2019] [Indexed: 12/22/2022] Open
Abstract
Environmental pressures caused by population growth and consumerism require the development of resource recovery from waste, hence a circular economy approach. The production of chemicals and fuels from organic waste using mixed microbial cultures (MMC) has become promising. MMC use the synergy of bio-catalytic activities from different microorganisms to transform complex organic feedstock, such as by-products from food production and food waste. In the absence of oxygen, the feedstock can be converted into biogas through the established anaerobic digestion (AD) approach. The potential of MMC has shifted to production of intermediate AD compounds as precursors for renewable chemicals. A particular set of anaerobic pathways in MMC fermentation, known as chain elongation, can occur under specific conditions producing medium chain carboxylic acids (MCCAs) with higher value than biogas and broader applicability. This review introduces the chain elongation pathway and other bio-reactions occurring during MMC fermentation. We present an overview of the complex feedstocks used, and pinpoint the main operational parameters for MCCAs production such as temperature, pH, loading rates, inoculum, head space composition, and reactor design. The review evaluates the key findings of MCCA production using MMC, and concludes by identifying critical research targets to drive forward this promising technology as a valorisation method for complex organic waste.
Collapse
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 Chemical 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.
- Water Innovation & Research Centre (WIRC), University of Bath, Claverton Down, Bath BA2 7AY, UK.
| | - David J Leak
- Centre for Sustainable Chemical Technologies (CSCT), 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.
| |
Collapse
|