1
|
Zhang Y, Liu B, Wu W, Liu H, Wang W. Propanol as electron donor for efficient odd-chain carboxylate production by chain elongation with reactor microbiomes. J Environ Sci (China) 2025; 156:849-858. [PMID: 40412981 DOI: 10.1016/j.jes.2024.12.033] [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: 07/19/2024] [Revised: 12/09/2024] [Accepted: 12/25/2024] [Indexed: 05/27/2025]
Abstract
Microbial consortia that catalyze chain elongation processes have been enriched using different selection strategies, for which the electron donor is an essential one. Propanol is an extraordinarily promising electron donor because it can be generated from renewable resources, including lignocellulosic biomass and protein wastes. Here, propanol was proven in detail to be an efficient electron donor, enhancing the production of odd medium-chain carboxylates during chain elongation. By exploring various electron acceptors, reactor conditions, and electron donor/electron acceptor mol ratios, our study highlights that acetate is the most suitable electron acceptor for the production of both odd- and even-chain carboxylates. The optimal conditions for propanol-based chain elongation were 30 °C and pH 6, achieving 82.8 % selectivity for odd-chain carboxylates. Another critical insight from our work is that a propanol/acetate mol ratio of 1:1 can minimize the inhibitory effect of propanol and maximize the yield of medium-chain carboxylates, with the highest concentration of n-heptanoate reaching 124.5 mmol C/L. This was further illustrated by 16S rRNA amplicon sequencing, which elucidated that the community composition and keystone species in a propanol-based reactor closely resembled that of the ethanol one. The dominant phylum of the propanol-based reactor, Firmicutes showed a significant positive correlation with the concentrations of n-caproate and n-valerate. Additionally, the co-occurrence of Clostridium sensu stricto 12 and Oscillibacter, known as typical chain elongators, was identified within the propanol-based reactor. These findings enhance our understanding of propanol-based chain elongation, offer guiding principles for reactor microbiota assembly, and support efficient odd medium-chain carboxylate production.
Collapse
Affiliation(s)
- Yanshen Zhang
- College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029, China; Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Bin Liu
- Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Wanling Wu
- College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029, China; Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Haopeng Liu
- College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Wen Wang
- Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
| |
Collapse
|
2
|
Suo M, Liu L, Fan H, Li N, Pan H, Hrynsphan D, Tatsiana S, Robles-Iglesias R, Wang Z, Chen J. Advancements in chain elongation technology: Transforming lactic acid into caproic acid for sustainable biochemical production. BIORESOURCE TECHNOLOGY 2025; 425:132312. [PMID: 40023331 DOI: 10.1016/j.biortech.2025.132312] [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: 05/21/2024] [Revised: 02/13/2025] [Accepted: 02/26/2025] [Indexed: 03/04/2025]
Abstract
This review provides an insight into the chain-elongation technology for the production of caproic acid, a chemical widely used in the food, pharmaceutical, and cosmetic industries, from lactic acid in waste organic matter. The evolution of the technology is traced, the reaction mechanism is elucidated, and the properties of key microbial agents capable of carrying out the chain-elongation technology are summarized and compared, including pure bacterial isolates and reactor-mixed microorganisms. Furthermore, the parameters that regulate caproic acid formation by influencing microbial activity, competitive pathways, product selection, and carbon flow distribution, such as pH, temperature, electron donor, electron acceptor, and hydrogen partial pressure, are highlighted and discussed. It is worth noting that various caproic acid product extraction technologies were also summarized and assessed. Finally, based on the perspective of interdisciplinary field, bold suggestions for the future research direction are put forward.
Collapse
Affiliation(s)
- Minyu Suo
- Key Laboratory of Pollution Exposure and Health Intervention of Zhejiang Province, Interdisciplinary Research Academy, Zhejiang Shuren University, Hangzhou 310015, China; College of Geography and Environmental Science, Zhejiang Normal University, Jinhua 321004, China
| | - Lingxiu Liu
- Key Laboratory of Pollution Exposure and Health Intervention of Zhejiang Province, Interdisciplinary Research Academy, Zhejiang Shuren University, Hangzhou 310015, China; College of Geography and Environmental Science, Zhejiang Normal University, Jinhua 321004, China
| | - Hongye Fan
- Key Laboratory of Pollution Exposure and Health Intervention of Zhejiang Province, Interdisciplinary Research Academy, Zhejiang Shuren University, Hangzhou 310015, China; College of Environment, Zhejiang University of Technology, Hangzhou 310014, China
| | - Nan Li
- Key Laboratory of Pollution Exposure and Health Intervention of Zhejiang Province, Interdisciplinary Research Academy, Zhejiang Shuren University, Hangzhou 310015, China; College of Environment, Zhejiang University of Technology, Hangzhou 310014, China
| | - Hua Pan
- Key Laboratory of Pollution Exposure and Health Intervention of Zhejiang Province, Interdisciplinary Research Academy, Zhejiang Shuren University, Hangzhou 310015, China
| | - Dzmitry Hrynsphan
- Research Institute of Physical and Chemical Problems, Belarusian State University, Minsk 220030, Belarus
| | - Savitskaya Tatsiana
- Research Institute of Physical and Chemical Problems, Belarusian State University, Minsk 220030, Belarus
| | - Raúl Robles-Iglesias
- Chemical Engineering Laboratory, Faculty of Sciences and Center for Advanced Scientific Research/Centro de Investigaciones Científicas Avanzadas (CICA), BIOENGIN Group, University of La Coruña, La Coruña 15008, Spain
| | - Zeyu Wang
- Key Laboratory of Pollution Exposure and Health Intervention of Zhejiang Province, Interdisciplinary Research Academy, Zhejiang Shuren University, Hangzhou 310015, China.
| | - Jun Chen
- Key Laboratory of Pollution Exposure and Health Intervention of Zhejiang Province, Interdisciplinary Research Academy, Zhejiang Shuren University, Hangzhou 310015, China.
| |
Collapse
|
3
|
Foka K, Ferousi C, Topakas E. Polyester-derived monomers as microbial feedstocks: Navigating the landscape of polyester upcycling. Biotechnol Adv 2025; 82:108589. [PMID: 40354902 DOI: 10.1016/j.biotechadv.2025.108589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2025] [Revised: 04/10/2025] [Accepted: 04/25/2025] [Indexed: 05/14/2025]
Abstract
Since their large-scale adoption in the early 20th century, plastics have become indispensable to modern life. However, inadequate disposal and recycling methods have led to severe environmental consequences. While traditional end-of-life plastics management had predominantly relied on landfilling, a paradigm shift towards recycling and valorization emerged in the 1970s, leading to the development of various, mostly mechanochemical, recycling strategies, together with the more recent approach of biological depolymerization and upcycling. Plastic upcycling, which converts plastic waste into higher-value products, is gaining attention as a sustainable strategy to reduce environmental impact and reliance on virgin materials. Microbial plastic upcycling relies on efficient depolymerization methods to generate monomeric substrates, which are subsequently metabolized by native or engineered microbial systems yielding valuable bioproducts. This review focuses on the second phase of microbial polyester upcycling, examining the intracellular metabolic pathways that enable the assimilation and bioconversion of polyester-derived monomers into industrially relevant compounds. Both biodegradable and non-biodegradable polyesters with commercial significance are considered, with emphasis on pure monomeric feedstocks to elucidate intracellular carbon assimilation pathways. Understanding these metabolic processes provides a foundation for future metabolic engineering efforts, aiming to optimize microbial systems for efficient bioconversion of mixed plastic hydrolysates into valuable bioproducts.
Collapse
Affiliation(s)
- Katerina Foka
- Industrial Biotechnology & Biocatalysis Group, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, 15772 Athens, Greece.
| | - Christina Ferousi
- Industrial Biotechnology & Biocatalysis Group, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, 15772 Athens, Greece.
| | - Evangelos Topakas
- Industrial Biotechnology & Biocatalysis Group, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, 15772 Athens, Greece.
| |
Collapse
|
4
|
Wang J, Zhu J, Wang X, Liu Z, Xu J, Wei C, Zhang R, Cai F, Zhu Z, Cao J, Yu Q. Enhanced production of ethyl caproate in strong-flavor Baijiu through a dual bacterial co-culture system and immobilization on natural luffa sponge. Food Res Int 2025; 208:116263. [PMID: 40263811 DOI: 10.1016/j.foodres.2025.116263] [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: 01/15/2025] [Revised: 02/13/2025] [Accepted: 03/11/2025] [Indexed: 04/24/2025]
Abstract
Ethyl caproate, a significant aromatic component in strong-flavor baijiu, is synthesized requiring caproic acid as an essential precursor. In this study, a novel caproic acid-producing bacteria Rummeliibacillus suwonensis J-1 was isolated from pit mud. Subsequently, a dual bacterial co-culture system (DBCS) was successfully established by combining J-1 with the acid-producing bacterium Enterococcus sp. D-1, resulting in a 21-fold increase in yield, which reached 4.41 g/L. A new immobilization strategy was developed, utilizing luffa sponge as a carrier for DBCS to facilitate pit mud-free strong-flavor baijiu production. The findings indicated a substantial increase in the ethyl caproate concentrations, with a 218 % increase, reaching 0.625 g/L. Transcriptomic analysis showed that in the two-bacterial system, crucial genes implicated in the biosynthesis pathway of caproic acid in J-1, including Crt, Scad, Ptb, pdxK, L-cysteine dehydrogenase, and l-serine decarboxylase were significantly upregulated, which enhanced the synthesis of caproic acid. These findings suggest that DBCS may have potential applications in fermentation without pit mud and could potentially enhance quality of strong-flavor baijiu.
Collapse
Affiliation(s)
- Jiangbo Wang
- Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Key Laboratory of Fermentation Engineering (Ministry of Education), Hubei Key Laboratory of Industrial Microbiology, School of Life and Health Sciences, Hubei University of Technology, 28 Nanli Road, Wuhan 430068, China
| | - Jiahao Zhu
- Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Key Laboratory of Fermentation Engineering (Ministry of Education), Hubei Key Laboratory of Industrial Microbiology, School of Life and Health Sciences, Hubei University of Technology, 28 Nanli Road, Wuhan 430068, China
| | - Xuan Wang
- Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Key Laboratory of Fermentation Engineering (Ministry of Education), Hubei Key Laboratory of Industrial Microbiology, School of Life and Health Sciences, Hubei University of Technology, 28 Nanli Road, Wuhan 430068, China
| | - Zhiwen Liu
- Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Key Laboratory of Fermentation Engineering (Ministry of Education), Hubei Key Laboratory of Industrial Microbiology, School of Life and Health Sciences, Hubei University of Technology, 28 Nanli Road, Wuhan 430068, China
| | - Jian Xu
- Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Key Laboratory of Fermentation Engineering (Ministry of Education), Hubei Key Laboratory of Industrial Microbiology, School of Life and Health Sciences, Hubei University of Technology, 28 Nanli Road, Wuhan 430068, China
| | - Chunhui Wei
- Liquor Making Biological Technology and Application of Key Laboratory of Sichuan Province, Sichuan University of Science & Engineering, 188 University Town Road, Yibin, 644000, China
| | - Ruijing Zhang
- Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Key Laboratory of Fermentation Engineering (Ministry of Education), Hubei Key Laboratory of Industrial Microbiology, School of Life and Health Sciences, Hubei University of Technology, 28 Nanli Road, Wuhan 430068, China
| | - Fengjiao Cai
- Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Key Laboratory of Fermentation Engineering (Ministry of Education), Hubei Key Laboratory of Industrial Microbiology, School of Life and Health Sciences, Hubei University of Technology, 28 Nanli Road, Wuhan 430068, China
| | - Zhengjun Zhu
- Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Key Laboratory of Fermentation Engineering (Ministry of Education), Hubei Key Laboratory of Industrial Microbiology, School of Life and Health Sciences, Hubei University of Technology, 28 Nanli Road, Wuhan 430068, China
| | - Jinghua Cao
- Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Key Laboratory of Fermentation Engineering (Ministry of Education), Hubei Key Laboratory of Industrial Microbiology, School of Life and Health Sciences, Hubei University of Technology, 28 Nanli Road, Wuhan 430068, China
| | - Qi Yu
- Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Key Laboratory of Fermentation Engineering (Ministry of Education), Hubei Key Laboratory of Industrial Microbiology, School of Life and Health Sciences, Hubei University of Technology, 28 Nanli Road, Wuhan 430068, China.
| |
Collapse
|
5
|
Wang Z, Chen J, Veiga MC, Kennes C. Enhancing caproate production in lactate-containing effluents by Megasphaera hexanoica through acetate modulation. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2025; 383:125327. [PMID: 40262499 DOI: 10.1016/j.jenvman.2025.125327] [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: 10/28/2024] [Revised: 02/26/2025] [Accepted: 04/10/2025] [Indexed: 04/24/2025]
Abstract
The anaerobic bacterium Megasphaera hexanoica has great potential for caproate production through reverse β-oxidation using lactate, acetate, and butyrate as substrates. This study assessed the effect of acetate concentrations (10-50 mM) on caproate biosynthesis, lactate oxidation, and cell synthesis in M. hexanoica. At 30 mM acetate, caproate production reached 42.83 mM, with an electron efficiency of 67.03 % and a specific productivity of 4.47 gCA·h-1·gDCW-1. Subsequent fed-batch experiments with lactate, acetate, and butyrate maintained continuous caproate production, achieving 65.21 mM. Bioreactor assays further validated the strategy, yielding 65.25 mM caproate over 180 h. Mechanistic analysis demonstrated that 30 mM acetate optimized acetyl-CoA flux and enhanced caproyl-CoA transferase activity (3.5 U‧mg-1), supporting caproate synthesis. Kinetic modeling demonstrated the Logistic model fit lactate consumption (R2 = 0.991), while the Fitzhugh model captured caproate production (R2 = 0.991, NRMSE = 1.137). The findings offer practical insights for industrial-scale caproate production.
Collapse
Affiliation(s)
- Zeyu Wang
- Key Laboratory of Pollution Exposure and Health Intervention of Zhejiang Province, Interdisciplinary Research Academy, Zhejiang Shuren University, Hangzhou, 310015, China; Chemical Engineering Laboratory, Faculty of Sciences and Interdisciplinary Centre of Chemistry and Biology - Centro Interdisciplinar de Química y Biología (CICA), BIOENGIN group, University of La Coruña (UDC), E-15008, La Coruña, Spain
| | - Jun Chen
- Key Laboratory of Pollution Exposure and Health Intervention of Zhejiang Province, Interdisciplinary Research Academy, Zhejiang Shuren University, Hangzhou, 310015, China
| | - María C Veiga
- Chemical Engineering Laboratory, Faculty of Sciences and Interdisciplinary Centre of Chemistry and Biology - Centro Interdisciplinar de Química y Biología (CICA), BIOENGIN group, University of La Coruña (UDC), E-15008, La Coruña, Spain
| | - Christian Kennes
- Chemical Engineering Laboratory, Faculty of Sciences and Interdisciplinary Centre of Chemistry and Biology - Centro Interdisciplinar de Química y Biología (CICA), BIOENGIN group, University of La Coruña (UDC), E-15008, La Coruña, Spain.
| |
Collapse
|
6
|
Wang Z, Chen J, Veiga MC, Kennes C. Scalable propionic acid production using Cutibacterium acnes ZW-1: Insights into substrate and pH-driven carbon flux. THE SCIENCE OF THE TOTAL ENVIRONMENT 2025; 967:178806. [PMID: 39946891 DOI: 10.1016/j.scitotenv.2025.178806] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2024] [Revised: 01/21/2025] [Accepted: 02/07/2025] [Indexed: 03/05/2025]
Abstract
An acid-resistant Cutibacterium acnes ZW-1 was isolated from human skin, and propionic acid (PA) production under different substrate and pH conditions was studied. When the molar ratio of lactic acid (LA) to acetic acid (AA) was 7:1 and the pH was 6.5, the PA concentration could reach 64.84 mM. Meanwhile, the index analysis and enzyme activity revealed that the PA carbon flux was 59 %, the PA electronic efficiency reached 79 %, and the propionyl-CoA carboxylase activity was 1.075 mmol·mg protein-1. Considering the competition between AA/PA production and biomass synthesis, although the slightly acidic pH (<6.5) would promote the flow of carbon to PA, its concentration was severely inhibited due to the limitation of biomass. Further scale-up verification in an automated bioreactor indicated that PA production improved, up to 83.31 mM, and the production rate reached 1.066 g·L-1·d-1. This work may provide support for the industrial application of PA bioproduction.
Collapse
Affiliation(s)
- Zeyu Wang
- Key Laboratory of Pollution Exposure and Health Intervention of Zhejiang Province, Interdisciplinary Research Academy, Zhejiang Shuren University, Hangzhou 310015, China; Chemical Engineering Laboratory, Faculty of Sciences and Interdisciplinary Centre of Chemistry and Biology - Centro Interdisciplinar de Química y Biología (CICA), BIOENGIN group, University of La Coruña (UDC), E-15008 La Coruña, Spain
| | - Jun Chen
- Key Laboratory of Pollution Exposure and Health Intervention of Zhejiang Province, Interdisciplinary Research Academy, Zhejiang Shuren University, Hangzhou 310015, China
| | - María C Veiga
- Chemical Engineering Laboratory, Faculty of Sciences and Interdisciplinary Centre of Chemistry and Biology - Centro Interdisciplinar de Química y Biología (CICA), BIOENGIN group, University of La Coruña (UDC), E-15008 La Coruña, Spain
| | - Christian Kennes
- Chemical Engineering Laboratory, Faculty of Sciences and Interdisciplinary Centre of Chemistry and Biology - Centro Interdisciplinar de Química y Biología (CICA), BIOENGIN group, University of La Coruña (UDC), E-15008 La Coruña, Spain.
| |
Collapse
|
7
|
Iglesias-Riobó J, Bonatelli ML, Machado-Fernández C, Mauricio-Iglesias M, Carballa M. Optimising medium chain carboxylate production in xylan mixed-culture monofermentation. BIORESOURCE TECHNOLOGY 2025; 420:132124. [PMID: 39880335 DOI: 10.1016/j.biortech.2025.132124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2024] [Revised: 01/14/2025] [Accepted: 01/26/2025] [Indexed: 01/31/2025]
Abstract
This work investigates the optimization of medium-chain carboxylate (MCC) production through xylan mixed-culture monofermentation. The pH screening in batch assays showed that the hydrolysis stage and selectivity towards MCC precursors were optimised at pH 6. Subsequently, a continuous stirred tank reactor (CSTR) and a Sequential Batch Reactor (SBR) were operated at different Hydraulic Retention Times (HRT), revealing that the SBR at HRT 2 days yielded the highest caproic acid since lactic acid availability and chain elongation process were balanced. An enriched medium with yeast extract and vitamins favoured the growth of chain elongators, and therefore, the MCC production. Moreover, cross-feeding interaction between bacteria in xylan fermentation was observed, and Pseudoramibacter was present in the highest caproic acid yields. This work highlights the impact of selecting the proper operational window to optimise one-stage MCC production.
Collapse
Affiliation(s)
- J Iglesias-Riobó
- CRETUS, Department of Chemical Engineering, Universidade de Santiago de Compostela 15782 Santiago de Compostela, Spain.
| | - M L Bonatelli
- Department of Microbial Biotechnology, Helmholtz Centre for Environmental Research - UFZ 04318 Leipzig, Germany; Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - C Machado-Fernández
- CRETUS, Department of Chemical Engineering, Universidade de Santiago de Compostela 15782 Santiago de Compostela, Spain
| | - M Mauricio-Iglesias
- CRETUS, Department of Chemical Engineering, Universidade de Santiago de Compostela 15782 Santiago de Compostela, Spain
| | - M Carballa
- CRETUS, Department of Chemical Engineering, Universidade de Santiago de Compostela 15782 Santiago de Compostela, Spain
| |
Collapse
|
8
|
Wang Y, Zhang X, Chen Y. The enhancement of caproic acid synthesis from organic solid wastes: A review. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2024; 371:123215. [PMID: 39504670 DOI: 10.1016/j.jenvman.2024.123215] [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: 06/20/2024] [Revised: 10/13/2024] [Accepted: 11/01/2024] [Indexed: 11/08/2024]
Abstract
Organic solid waste (OSW) significantly harms the environment and threatens human health. Producing caproic acid (CA) from OSW presents a cost-effective, sustainable, and resource-efficient solution. This study comprehensively examines the various methods for synthesizing CA from OSW, focusing on waste material selection, pretreatment processes to improve dissolution and hydrolysis of OSW, key substrates, and optimization strategies. Using OSW resources has been extensively studied and applied across numerous industries, presenting a promising solution for reducing environmental pollution. This study provides insights into CA synthesis pathways and substrate selection while emphasizing the optimization of CA production from OSW. It also highlights key areas for future research.
Collapse
Affiliation(s)
- Yidan Wang
- State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai, 200092, China
| | - Xuemeng Zhang
- State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai, 200092, China
| | - Yinguang Chen
- State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai, 200092, China.
| |
Collapse
|
9
|
Ma H, Liu Y, Zhao J, Fei F, Gao M, Wang Q. Explainable machine learning-driven predictive performance and process parameter optimization for caproic acid production. BIORESOURCE TECHNOLOGY 2024; 410:131311. [PMID: 39168415 DOI: 10.1016/j.biortech.2024.131311] [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: 06/26/2024] [Revised: 08/15/2024] [Accepted: 08/17/2024] [Indexed: 08/23/2024]
Abstract
In this study, four machine learning (ML) prediction models were developed to predict and optimize the production performance of caproic acid based on substrates, products, and process parameters. The XGBoost outperformed others, with a high R2 of 0.998 on the training set and 0.885 on the test set. Feature importance analysis revealed hydraulic retention time (HRT) and butyric acid concentration are decisive. The SHAP method offered profound insights into the interplay and cumulative effects of substrate composition, identified the synergistic effects between butyric acid and lactic acid, and emphasized adding glucose can benefit caproic with lactic acid co-fermentation. By integrating the Adaptive Variation Particle Swarm Optimization (AVPSO) algorithm, the optimal process conditions to achieve a maximum caproic acid production of 8.64 g/L was obtained. This study not only advances caproic acid production but contributes a versatile ML-driven strategy applicable to bioprocess optimizations, potentially transformative for sustainable and economically viable bioproduction.
Collapse
Affiliation(s)
- Hongzhi Ma
- Department of Environmental Science and Engineering, University of Science and Technology Beijing, Beijing Key Laboratory of Resource-oriented Treatment of Industrial Pollutants, 100083, China; Xinjiang Key Laboratory of Clean Conversion and High Value Utilization of Biomass Resources, School of Resource and Environmental Science, Yili Normal University, Yining 835000, China.
| | - Yichan Liu
- Department of Environmental Science and Engineering, University of Science and Technology Beijing, Beijing Key Laboratory of Resource-oriented Treatment of Industrial Pollutants, 100083, China
| | - Jihua Zhao
- Department of Environmental Science and Engineering, University of Science and Technology Beijing, Beijing Key Laboratory of Resource-oriented Treatment of Industrial Pollutants, 100083, China
| | - Fan Fei
- Department of Environmental Science and Engineering, University of Science and Technology Beijing, Beijing Key Laboratory of Resource-oriented Treatment of Industrial Pollutants, 100083, China
| | - Ming Gao
- Department of Environmental Science and Engineering, University of Science and Technology Beijing, Beijing Key Laboratory of Resource-oriented Treatment of Industrial Pollutants, 100083, China
| | - Qunhui Wang
- Department of Environmental Science and Engineering, University of Science and Technology Beijing, Beijing Key Laboratory of Resource-oriented Treatment of Industrial Pollutants, 100083, China
| |
Collapse
|
10
|
Bian B, Zhang W, Yu N, Yang W, Xu J, Logan BE, Saikaly PE. Lactate-mediated medium-chain fatty acid production from expired dairy and beverage waste. ENVIRONMENTAL SCIENCE AND ECOTECHNOLOGY 2024; 21:100424. [PMID: 38774191 PMCID: PMC11106833 DOI: 10.1016/j.ese.2024.100424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Revised: 04/18/2024] [Accepted: 04/18/2024] [Indexed: 05/24/2024]
Abstract
Fruits, vegetables, and dairy products are typically the primary sources of household food waste. Currently, anaerobic digestion is the most used bioprocess for the treatment of food waste with concomitant generation of biogas. However, to achieve a circular carbon economy, the organics in food waste should be converted to new chemicals with higher value than energy. Here we demonstrate the feasibility of medium-chain carboxylic acid (MCCA) production from expired dairy and beverage waste via a chain elongation platform mediated by lactate. In a two-stage fermentation process, the first stage with optimized operational conditions, including varying temperatures and organic loading rates, transformed expired dairy and beverage waste into lactate at a concentration higher than 900 mM C at 43 °C. This lactate was then used to produce >500 mM C caproate and >300 mM C butyrate via microbial chain elongation. Predominantly, lactate-producing microbes such as Lactobacillus and Lacticaseibacillus were regulated by temperature and could be highly enriched under mesophilic conditions in the first-stage reactor. In the second-stage chain elongation reactor, the dominating microbes were primarily from the genera Megasphaera and Caproiciproducens, shaped by varying feed and inoculum sources. Co-occurrence network analysis revealed positive correlations among species from the genera Caproiciproducens, Ruminococcus, and CAG-352, as well as Megasphaera, Bacteroides, and Solobacterium, indicating strong microbial interactions that enhance caproate production. These findings suggest that producing MCCAs from expired dairy and beverage waste via lactate-mediated chain elongation is a viable method for sustainable waste management and could serve as a chemical production platform in the context of building a circular bioeconomy.
Collapse
Affiliation(s)
- Bin Bian
- Water Desalination and Reuse Center (WDRC), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
- Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Wenxiang Zhang
- Water Desalination and Reuse Center (WDRC), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
- Research Centre of Ecology & Environment for Coastal Area and Deep Sea, Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, 511458, China
| | - Najiaowa Yu
- Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Wei Yang
- Water Desalination and Reuse Center (WDRC), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Jiajie Xu
- Water Desalination and Reuse Center (WDRC), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
- School of Marine Science, Ningbo University, Ningbo, 315211, China
| | - Bruce E. Logan
- Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Pascal E. Saikaly
- Water Desalination and Reuse Center (WDRC), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
- Environmental Science and Engineering Program, Biological and Environmental Science and Engineering (BESE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
| |
Collapse
|
11
|
Liu Y, Ye X, Chen K, Wu X, Jiao L, Zhang H, Zhu F, Xi Y. Effect of nanobubble water on medium chain carboxylic acids production in anaerobic digestion of cow manure. WASTE MANAGEMENT (NEW YORK, N.Y.) 2024; 184:37-51. [PMID: 38795539 DOI: 10.1016/j.wasman.2024.05.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Revised: 04/30/2024] [Accepted: 05/20/2024] [Indexed: 05/28/2024]
Abstract
Nanobubble water promotes the degradation of difficult-to-degrade organic matter, improves the activity of electron transfer systems during anaerobic digestion, and optimizes the composition of anaerobic microbial communities. Therefore, this study proposes the use of nanobubble water to improve the yield of medium chain carboxylic acids produced from cow manure by chain elongation. The experiment was divided into two stages: the first stage involved the acidification of cow manure to produce volatile acidic fatty acids as electron acceptors, and the second phase involved the addition of lactic acid as an electron donor for the chain elongation. Three experimental groups were established, and air, H2, and N2 nanobubble water were added in the second stage. Equal amounts of deionized water were added in the control group. The results showed that nanobubble water supplemented with air significantly increased the caproic acid concentration to 15.10 g/L, which was 55.03 % greater than that of the control group. The relative abundances of Bacillus and Caproiciproducens, which are involved in chain elongation, and Syntrophomonas, which is involved in electron transfer, increased. The unique ability of air nanobubble water supplemented to break down the cellulose matrix resulted in further decomposition of the recalcitrant material in cow manure. This effect subsequently increased the number of microorganisms associated with lignocellulose degradation, increasing carbohydrate metabolism and ATP-binding cassette transporter protein activity and enhancing fatty acid cycling pathways during chain elongation. Ultimately, this approach enabled the efficient production of medium chain carboxylic acids.
Collapse
Affiliation(s)
- Yang Liu
- Jiangsu Academy of Agriculture Sciences, Nanjing 210014, China; Key Laboratory of Crop and Livestock Integration, Ministry of Agriculture and Rural Affairs, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, 210014 Nanjing, China; State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical, Nanjing Tech University, Nanjing 210009, China
| | - Xiaomei Ye
- Jiangsu Academy of Agriculture Sciences, Nanjing 210014, China; Key Laboratory of Crop and Livestock Integration, Ministry of Agriculture and Rural Affairs, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, 210014 Nanjing, China
| | - Kequan Chen
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical, Nanjing Tech University, Nanjing 210009, China
| | - Xiayuan Wu
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical, Nanjing Tech University, Nanjing 210009, China
| | - Lihua Jiao
- Jiangsu Academy of Agriculture Sciences, Nanjing 210014, China; Key Laboratory of Crop and Livestock Integration, Ministry of Agriculture and Rural Affairs, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, 210014 Nanjing, China
| | - Hongyu Zhang
- Jiangsu Academy of Agriculture Sciences, Nanjing 210014, China; Key Laboratory of Crop and Livestock Integration, Ministry of Agriculture and Rural Affairs, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, 210014 Nanjing, China
| | - Fei Zhu
- Jiangsu Academy of Agriculture Sciences, Nanjing 210014, China; Key Laboratory of Crop and Livestock Integration, Ministry of Agriculture and Rural Affairs, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, 210014 Nanjing, China
| | - Yonglan Xi
- Jiangsu Academy of Agriculture Sciences, Nanjing 210014, China; Key Laboratory of Crop and Livestock Integration, Ministry of Agriculture and Rural Affairs, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, 210014 Nanjing, China; Department of Applied Ecology, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcka 129, Praha-Suchdol 16500, Czech Republic.
| |
Collapse
|
12
|
Liu Y, Duan Y, Chen L, Yang Z, Yang X, Liu S, Song G. Research on the Resource Recovery of Medium-Chain Fatty Acids from Municipal Sludge: Current State and Future Prospects. Microorganisms 2024; 12:680. [PMID: 38674623 PMCID: PMC11051992 DOI: 10.3390/microorganisms12040680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2024] [Revised: 03/26/2024] [Accepted: 03/27/2024] [Indexed: 04/28/2024] Open
Abstract
The production of municipal sludge is steadily increasing in line with the production of sewage. A wealth of organic contaminants, including nutrients and energy, are present in municipal sludge. Anaerobic fermentation can be used to extract useful resources from sludge, producing hydrogen, methane, short-chain fatty acids, and, via further chain elongation, medium-chain fatty acids. By comparing the economic and use values of these retrieved resources, it is concluded that a high-value resource transformation of municipal sludge can be achieved via the production of medium-chain fatty acids using anaerobic fermentation, which is a hotspot for future research. In this study, the selection of the pretreatment method, the method of producing medium-chain fatty acids, the influence of the electron donor, and the technique used to enhance product synthesis in the anaerobic fermentation process are introduced in detail. The study outlines potential future research directions for medium-chain fatty acid production using municipal sludge. These acids could serve as a starting point for investigating other uses for municipal sludge.
Collapse
Affiliation(s)
- Yuhao Liu
- School of Environmental and Municipal Engineering, North China University of Water Resources and Electric Power, Zhengzhou 450046, China; (Y.D.); (L.C.); (Z.Y.); (X.Y.); (S.L.); (G.S.)
| | | | | | | | | | | | | |
Collapse
|
13
|
Wang Z, Fernández-Blanco C, Chen J, Veiga MC, Kennes C. Effect of electron acceptors on product selectivity and carbon flux in carbon chain elongation with Megasphaera hexanoica. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 912:169509. [PMID: 38141983 DOI: 10.1016/j.scitotenv.2023.169509] [Citation(s) in RCA: 24] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Revised: 12/14/2023] [Accepted: 12/17/2023] [Indexed: 12/25/2023]
Abstract
Megasphaera hexanoica is a bacterial strain following the reverse β-oxidation pathway to synthesize caproate (CA) using lactate (LA) as an electron donor (ED) and acetate (AA) or butyrate (BA) as electron acceptors (EA). Differences in the type and concentration of EA lead to distinctions in product distribution and energy bifurcation of carbon fluxes in ED pathways, thereby affecting CA production. In this study, the effect of various ratios of AA, BA, and AA+BA as EA on carbon flux and CA specific titer during the carbon chain elongation in M. hexanoica was explored. The results indicated that the maximum levels of CA were 18.81 mM and 31.48 mM when the molar ratios of LA/AA and LA/BA were 10:1 and 3:1, respectively. Meanwhile, when AA and BA were used as combined EA (LA, AA, and BA molar amounts of 100, 23, and 77 mM), a maximum CA production of 39.45 mM was obtained. Further analysis revealed that the combined EA exhibited a CA production carbon flux of 49 % (4.3 % and 19.5 % higher compared to AA or BA, respectively) and a CA production specific titer of 45.24 mol (80.89 % and 58.51 % higher compared to AA or BA, respectively), indicating that the effective carbon utilization rate and CA production efficiency were greatly improved. Finally, a scaled-up experiment was conducted in a 1.2 L (working volume) automated bioreactor, implying high biomass (optical density at 600 nm or OD600 = 1.809) and a slight decrease in CA production (28.45 mM). A decrease in H2 production (4.11 g/m3) and an increase in CO2 production (0.632 g/m3) demonstrated the appropriate metabolic adaptation of M. hexanoica to environmental changes such as stirring shear.
Collapse
Affiliation(s)
- Zeyu Wang
- Chemical Engineering Laboratory, Faculty of Sciences and Interdisciplinary Centre of Chemistry and Biology - Centro Interdisciplinar de Química y Biología (CICA), BIOENGIN group, University of La Coruña (UDC), E-15008 La Coruña, Spain; Key Laboratory of Pollution Exposure and Health Intervention of Zhejiang Province, Interdisciplinary Research Academy, Zhejiang Shuren University, Hangzhou 310015, China
| | - Carla Fernández-Blanco
- Chemical Engineering Laboratory, Faculty of Sciences and Interdisciplinary Centre of Chemistry and Biology - Centro Interdisciplinar de Química y Biología (CICA), BIOENGIN group, University of La Coruña (UDC), E-15008 La Coruña, Spain
| | - Jun Chen
- Key Laboratory of Pollution Exposure and Health Intervention of Zhejiang Province, Interdisciplinary Research Academy, Zhejiang Shuren University, Hangzhou 310015, China
| | - María C Veiga
- Chemical Engineering Laboratory, Faculty of Sciences and Interdisciplinary Centre of Chemistry and Biology - Centro Interdisciplinar de Química y Biología (CICA), BIOENGIN group, University of La Coruña (UDC), E-15008 La Coruña, Spain
| | - Christian Kennes
- Chemical Engineering Laboratory, Faculty of Sciences and Interdisciplinary Centre of Chemistry and Biology - Centro Interdisciplinar de Química y Biología (CICA), BIOENGIN group, University of La Coruña (UDC), E-15008 La Coruña, Spain.
| |
Collapse
|
14
|
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.
Collapse
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
| |
Collapse
|
15
|
Romans-Casas M, Feliu-Paradeda L, Tedesco M, Hamelers HV, Bañeras L, Balaguer MD, Puig S, Dessì P. Selective butyric acid production from CO 2 and its upgrade to butanol in microbial electrosynthesis cells. ENVIRONMENTAL SCIENCE AND ECOTECHNOLOGY 2024; 17:100303. [PMID: 37635954 PMCID: PMC10457423 DOI: 10.1016/j.ese.2023.100303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 07/16/2023] [Accepted: 07/22/2023] [Indexed: 08/29/2023]
Abstract
Microbial electrosynthesis (MES) is a promising carbon utilization technology, but the low-value products (i.e., acetate or methane) and the high electric power demand hinder its industrial adoption. In this study, electrically efficient MES cells with a low ohmic resistance of 15.7 mΩ m2 were operated galvanostatically in fed-batch mode, alternating periods of high CO2 and H2 availability. This promoted acetic acid and ethanol production, ultimately triggering selective (78% on a carbon basis) butyric acid production via chain elongation. An average production rate of 14.5 g m-2 d-1 was obtained at an applied current of 1.0 or 1.5 mA cm-2, being Megasphaera sp. the key chain elongating player. Inoculating a second cell with the catholyte containing the enriched community resulted in butyric acid production at the same rate as the previous cell, but the lag phase was reduced by 82%. Furthermore, interrupting the CO2 feeding and setting a constant pH2 of 1.7-1.8 atm in the cathode compartment triggered solventogenic butanol production at a pH below 4.8. The efficient cell design resulted in average cell voltages of 2.6-2.8 V and a remarkably low electric energy requirement of 34.6 kWhel kg-1 of butyric acid produced, despite coulombic efficiencies being restricted to 45% due to the cross-over of O2 and H2 through the membrane. In conclusion, this study revealed the optimal operating conditions to achieve energy-efficient butyric acid production from CO2 and suggested a strategy to further upgrade it to valuable butanol.
Collapse
Affiliation(s)
- Meritxell Romans-Casas
- LEQUiA, Institute of the Environment, University of Girona. Campus Montilivi, Carrer Maria Aurèlia Capmany 69, E-17003, Girona, Spain
| | - Laura Feliu-Paradeda
- Molecular Microbial Ecology Group, Institute of Aquatic Ecology, University of Girona, Maria Aurèlia Capmany 40, 17003, Girona, Spain
| | - Michele Tedesco
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911, MA, Leeuwarden, the Netherlands
| | - Hubertus V.M. Hamelers
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911, MA, Leeuwarden, the Netherlands
| | - Lluis Bañeras
- Molecular Microbial Ecology Group, Institute of Aquatic Ecology, University of Girona, Maria Aurèlia Capmany 40, 17003, Girona, Spain
| | - M. Dolors Balaguer
- LEQUiA, Institute of the Environment, University of Girona. Campus Montilivi, Carrer Maria Aurèlia Capmany 69, E-17003, Girona, Spain
| | - Sebastià Puig
- LEQUiA, Institute of the Environment, University of Girona. Campus Montilivi, Carrer Maria Aurèlia Capmany 69, E-17003, Girona, Spain
| | - Paolo Dessì
- LEQUiA, Institute of the Environment, University of Girona. Campus Montilivi, Carrer Maria Aurèlia Capmany 69, E-17003, Girona, Spain
| |
Collapse
|
16
|
Fernández-Blanco C, Veiga MC, Kennes C. Effect of pH and medium composition on chain elongation with Megasphaera hexanoica producing C 4-C 8 fatty acids. Front Microbiol 2023; 14:1281103. [PMID: 38029098 PMCID: PMC10653306 DOI: 10.3389/fmicb.2023.1281103] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 10/17/2023] [Indexed: 12/01/2023] Open
Abstract
Introduction Chain elongation technology, which involves fermentation with anaerobic bacteria, has gained attention for converting short and medium chain substrates into valuable and longer-chain products like medium chain fatty acids (MCFAs). In the recent past, the focus of studies with pure chain elongating cultures was on species of other genera, mainly Clostridium kluyveri. Recently, other chain elongators have been isolated that deserve further research, such as Megasphaera hexanoica. Methods In this study, batch studies were performed in bottles with two different media to establish the optimal conditions for growth of M. hexanoica: (a) a medium rich in different sources of nitrogen and (b) a medium whose only source of nitrogen is yeast extract. Also, batch bioreactor studies at pH values of 5.8, 6.5 and 7.2 were set up to study the fermentation of lactate (i.e., electron donor) and acetate (i.e., electron acceptor) by M. hexanoica. Results and discussion Batch bottle studies revealed the yeast extract (YE) containing medium as the most promising in terms of production/cost ratio, producing n-caproate rapidly up to 2.62 ± 0.24 g/L. Subsequent bioreactor experiments at pH 5.8, 6.5, and 7.2 confirmed consistent production profiles, yielding C4-C8 fatty acids. A fourth bioreactor experiment at pH 6.5 and doubling both lactate and acetate concentrations enhanced MCFA production, resulting in 3.7 g/L n-caproate and 1.5 g/L n-caprylate. H2 and CO2 production was observed in all fermentations, being especially high under the increased substrate conditions. Overall, this study provides insights into M. hexanoica's behavior in lactate-based chain elongation and highlights optimization potential for improved productivity.
Collapse
Affiliation(s)
| | | | - Christian Kennes
- Chemical Engineering Laboratory, Faculty of Sciences and Interdisciplinary Centre of Chemistry and Biology – Centro Interdisciplinar de Química y Biología (CICA), BIOENGIN Group, University of A Coruña, Coruña, Spain
| |
Collapse
|
17
|
Candry P, Chadwick GL, Caravajal-Arroyo JM, Lacoere T, Winkler MKH, Ganigué R, Orphan VJ, Rabaey K. Trophic interactions shape the spatial organization of medium-chain carboxylic acid producing granular biofilm communities. THE ISME JOURNAL 2023; 17:2014-2022. [PMID: 37715042 PMCID: PMC10579388 DOI: 10.1038/s41396-023-01508-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Revised: 08/30/2023] [Accepted: 08/31/2023] [Indexed: 09/17/2023]
Abstract
Granular biofilms producing medium-chain carboxylic acids (MCCA) from carbohydrate-rich industrial feedstocks harbor highly streamlined communities converting sugars to MCCA either directly or via lactic acid as intermediate. We investigated the spatial organization and growth activity patterns of MCCA producing granular biofilms grown on an industrial side stream to test (i) whether key functional guilds (lactic acid producing Olsenella and MCCA producing Oscillospiraceae) stratified in the biofilm based on substrate usage, and (ii) whether spatial patterns of growth activity shaped the unique, lenticular morphology of these biofilms. First, three novel isolates (one Olsenella and two Oscillospiraceae species) representing over half of the granular biofilm community were obtained and used to develop FISH probes, revealing that key functional guilds were not stratified. Instead, the outer 150-500 µm of the granular biofilm consisted of a well-mixed community of Olsenella and Oscillospiraceae, while deeper layers were made up of other bacteria with lower activities. Second, nanoSIMS analysis of 15N incorporation in biofilms grown in normal and lactic acid amended conditions suggested Oscillospiraceae switched from sugars to lactic acid as substrate. This suggests competitive-cooperative interactions may govern the spatial organization of these biofilms, and suggests that optimizing biofilm size may be a suitable process engineering strategy. Third, growth activities were similar in the polar and equatorial biofilm peripheries, leaving the mechanism behind the lenticular biofilm morphology unexplained. Physical processes (e.g., shear hydrodynamics, biofilm life cycles) may have contributed to lenticular biofilm development. Together, this study develops an ecological framework of MCCA-producing granular biofilms that informs bioprocess development.
Collapse
Affiliation(s)
- Pieter Candry
- Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, 9000, Ghent, Belgium
- Civil and Environmental Engineering, University of Washington, 201 More Hall, Box 352700, Seattle, WA, 98195-2700, USA
| | - Grayson L Chadwick
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, 91125, USA
| | - José Maria Caravajal-Arroyo
- Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, 9000, Ghent, Belgium
| | - Tim Lacoere
- Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, 9000, Ghent, Belgium
| | | | - Ramon Ganigué
- Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, 9000, Ghent, Belgium
- Center for Advanced Processes and Technology for Urban Resource Recovery (CAPTURE), Frieda Saeysstraat 1, 9000, Ghent, Belgium
| | - Victoria J Orphan
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Korneel Rabaey
- Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, 9000, Ghent, Belgium.
- Center for Advanced Processes and Technology for Urban Resource Recovery (CAPTURE), Frieda Saeysstraat 1, 9000, Ghent, Belgium.
| |
Collapse
|
18
|
Lee GH, Kim DW, Jin YH, Kim SM, Lim ES, Cha MJ, Ko JK, Gong G, Lee SM, Um Y, Han SO, Ahn JH. Biotechnological Plastic Degradation and Valorization Using Systems Metabolic Engineering. Int J Mol Sci 2023; 24:15181. [PMID: 37894861 PMCID: PMC10607142 DOI: 10.3390/ijms242015181] [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: 09/22/2023] [Revised: 10/10/2023] [Accepted: 10/13/2023] [Indexed: 10/29/2023] Open
Abstract
Various kinds of plastics have been developed over the past century, vastly improving the quality of life. However, the indiscriminate production and irresponsible management of plastics have led to the accumulation of plastic waste, emerging as a pressing environmental concern. To establish a clean and sustainable plastic economy, plastic recycling becomes imperative to mitigate resource depletion and replace non-eco-friendly processes, such as incineration. Although chemical and mechanical recycling technologies exist, the prevalence of composite plastics in product manufacturing complicates recycling efforts. In recent years, the biodegradation of plastics using enzymes and microorganisms has been reported, opening a new possibility for biotechnological plastic degradation and bio-upcycling. This review provides an overview of microbial strains capable of degrading various plastics, highlighting key enzymes and their role. In addition, recent advances in plastic waste valorization technology based on systems metabolic engineering are explored in detail. Finally, future perspectives on systems metabolic engineering strategies to develop a circular plastic bioeconomy are discussed.
Collapse
Affiliation(s)
- Ga Hyun Lee
- Clean Energy Research Center, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea
- Department of Biotechnology, Korea University, Seoul 02841, Republic of Korea
| | - Do-Wook Kim
- Clean Energy Research Center, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea
| | - Yun Hui Jin
- Clean Energy Research Center, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea
- Department of Biotechnology, Korea University, Seoul 02841, Republic of Korea
| | - Sang Min Kim
- Clean Energy Research Center, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea
- Department of Biotechnology, Korea University, Seoul 02841, Republic of Korea
| | - Eui Seok Lim
- Clean Energy Research Center, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea
- Department of Biotechnology, Korea University, Seoul 02841, Republic of Korea
| | - Min Ji Cha
- Clean Energy Research Center, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea
- Department of Biotechnology, Korea University, Seoul 02841, Republic of Korea
| | - Ja Kyong Ko
- Clean Energy Research Center, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea
- Division of Energy and Environment Technology, KIST School, University of Science and Technology (UST), Daejeon 34113, Republic of Korea
| | - Gyeongtaek Gong
- Clean Energy Research Center, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea
- Division of Energy and Environment Technology, KIST School, University of Science and Technology (UST), Daejeon 34113, Republic of Korea
| | - Sun-Mi Lee
- Clean Energy Research Center, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea
- Division of Energy and Environment Technology, KIST School, University of Science and Technology (UST), Daejeon 34113, Republic of Korea
| | - Youngsoon Um
- Clean Energy Research Center, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea
- Division of Energy and Environment Technology, KIST School, University of Science and Technology (UST), Daejeon 34113, Republic of Korea
| | - Sung Ok Han
- Department of Biotechnology, Korea University, Seoul 02841, Republic of Korea
| | - Jung Ho Ahn
- Clean Energy Research Center, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea
- Division of Energy and Environment Technology, KIST School, University of Science and Technology (UST), Daejeon 34113, Republic of Korea
| |
Collapse
|
19
|
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
|
20
|
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.
Collapse
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.
| |
Collapse
|
21
|
Dahiya S, Mohan SV. Co-fermenting lactic acid and glucose towards caproic acid production. CHEMOSPHERE 2023; 328:138491. [PMID: 36963586 DOI: 10.1016/j.chemosphere.2023.138491] [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: 08/25/2022] [Revised: 02/20/2023] [Accepted: 03/21/2023] [Indexed: 06/18/2023]
Abstract
The functional role of lactate (HLac), as a co-substrate along with glucose (Glu) as well as an electron donor for the synthesis of caproic acid (HCa), a medium chain fatty acid (MCFAs) was studied. A varied HLac and Glu ratios were thus investigated in fed-batch anaerobic reactors (R1-R5) operated at pH 6 with a heat-treated anaerobic consortium. R1 and R5 were noted as controls and operated with sole Glu and HLac, respectively. Strategically, ethanol (HEth) was additionally supplemented as co-electron donor after the production of short chain carboxylic acids (SCCAs) for chain elongation in all the reactors. The reactor operated with HLac and Glu in a ratio of 0.25:0.75 (1.25 g/L (HLac) and 3.75 g/L (Glu)) showed the highest HCa production of 1.86 g/L. R5 operated with solely HLac yielded propionic acid (HPr) as the major product which further led to the higher valeric acid (HVa) production of 1.1 g/L within the reactor. Butyric acid (HBu) was observed in R1, which used Glu as carbon source alone indicating the importance of HLac as electron co-donor. Clostridium observed as the most dominant genera in shotgun metagenome sequencing in R2 and R3, the reactors that produced the highest HCa in comparison to other studied reactors. The study thus provided insight into the importance of substrate and electron donor and their supplementation strategies during the production of MCFAs.
Collapse
Affiliation(s)
- Shikha Dahiya
- Bioengineering and Environmental Science Lab, Department of Energy and Environmental Engineering, CSIR-Indian Institute of Chemical Technology (CSIR-IICT), Hyderabad, 500 007, India; Academy of Scientific & Innovative Research (AcSIR), Ghaziabad, 201002, India
| | - S Venkata Mohan
- Bioengineering and Environmental Science Lab, Department of Energy and Environmental Engineering, CSIR-Indian Institute of Chemical Technology (CSIR-IICT), Hyderabad, 500 007, India; Academy of Scientific & Innovative Research (AcSIR), Ghaziabad, 201002, India.
| |
Collapse
|
22
|
Myers KS, Ingle AT, Walters KA, Fortney NW, Scarborough MJ, Donohue TJ, Noguera DR. Comparison of metagenomes from fermentation of various agroindustrial residues suggests a common model of community organization. Front Bioeng Biotechnol 2023; 11:1197175. [PMID: 37260833 PMCID: PMC10228549 DOI: 10.3389/fbioe.2023.1197175] [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: 03/30/2023] [Accepted: 04/27/2023] [Indexed: 06/02/2023] Open
Abstract
The liquid residue resulting from various agroindustrial processes is both rich in organic material and an attractive source to produce a variety of chemicals. Using microbial communities to produce chemicals from these liquid residues is an active area of research, but it is unclear how to deploy microbial communities to produce specific products from the different agroindustrial residues. To address this, we fed anaerobic bioreactors one of several agroindustrial residues (carbohydrate-rich lignocellulosic fermentation conversion residue, xylose, dairy manure hydrolysate, ultra-filtered milk permeate, and thin stillage from a starch bioethanol plant) and inoculated them with a microbial community from an acid-phase digester operated at the wastewater treatment plant in Madison, WI, United States. The bioreactors were monitored over a period of months and sampled to assess microbial community composition and extracellular fermentation products. We obtained metagenome assembled genomes (MAGs) from the microbial communities in each bioreactor and performed comparative genomic analyses to identify common microorganisms, as well as any community members that were unique to each reactor. Collectively, we obtained a dataset of 217 non-redundant MAGs from these bioreactors. This metagenome assembled genome dataset was used to evaluate whether a specific microbial ecology model in which medium chain fatty acids (MCFAs) are simultaneously produced from intermediate products (e.g., lactic acid) and carbohydrates could be applicable to all fermentation systems, regardless of the feedstock. MAGs were classified using a multiclass classification machine learning algorithm into three groups, organisms fermenting the carbohydrates to intermediate products, organisms utilizing the intermediate products to produce MCFAs, and organisms producing MCFAs directly from carbohydrates. This analysis revealed common biological functions among the microbial communities in different bioreactors, and although different microorganisms were enriched depending on the agroindustrial residue tested, the results supported the conclusion that the microbial ecology model tested was appropriate to explain the MCFA production potential from all agricultural residues.
Collapse
Affiliation(s)
- Kevin S. Myers
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI, United States
- Wisconsin Energy Institute, University of Wisconsin-Madison, Madison, WI, United States
| | - Abel T. Ingle
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI, United States
- Wisconsin Energy Institute, University of Wisconsin-Madison, Madison, WI, United States
- Department of Civil and Environmental Engineering, University of Wisconsin-Madison, Madison, WI, United States
| | - Kevin A. Walters
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI, United States
- Wisconsin Energy Institute, University of Wisconsin-Madison, Madison, WI, United States
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, United States
| | - Nathaniel W. Fortney
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI, United States
- Wisconsin Energy Institute, University of Wisconsin-Madison, Madison, WI, United States
| | - Matthew J. Scarborough
- Department of Civil and Environmental Engineering, University of Vermont, Burlington, VT, United States
| | - Timothy J. Donohue
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI, United States
- Wisconsin Energy Institute, University of Wisconsin-Madison, Madison, WI, United States
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, United States
| | - Daniel R. Noguera
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI, United States
- Wisconsin Energy Institute, University of Wisconsin-Madison, Madison, WI, United States
- Department of Civil and Environmental Engineering, University of Wisconsin-Madison, Madison, WI, United States
| |
Collapse
|
23
|
Garces Daza F, Haitz F, Born A, Boles E. An optimized reverse β-oxidation pathway to produce selected medium-chain fatty acids in Saccharomyces cerevisiae. BIOTECHNOLOGY FOR BIOFUELS AND BIOPRODUCTS 2023; 16:71. [PMID: 37101299 PMCID: PMC10134560 DOI: 10.1186/s13068-023-02317-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Accepted: 04/06/2023] [Indexed: 04/28/2023]
Abstract
BACKGROUND Medium-chain fatty acids are molecules with applications in different industries and with growing demand. However, the current methods for their extraction are not environmentally sustainable. The reverse β-oxidation pathway is an energy-efficient pathway that produces medium-chain fatty acids in microorganisms, and its use in Saccharomyces cerevisiae, a broadly used industrial microorganism, is desired. However, the application of this pathway in this organism has so far either led to low titers or to the predominant production of short-chain fatty acids. RESULTS We genetically engineered Saccharomyces cerevisiae to produce the medium-chain fatty acids hexanoic and octanoic acid using novel variants of the reverse β-oxidation pathway. We first knocked out glycerolphosphate dehydrogenase GPD2 in an alcohol dehydrogenases knock-out strain (△adh1-5) to increase the NADH availability for the pathway, which significantly increased the production of butyric acid (78 mg/L) and hexanoic acid (2 mg/L) when the pathway was expressed from a plasmid with BktB as thiolase. Then, we tested different enzymes for the subsequent pathway reactions: the 3-hydroxyacyl-CoA dehydrogenase PaaH1 increased hexanoic acid production to 33 mg/L, and the expression of enoyl-CoA hydratases Crt2 or Ech was critical to producing octanoic acid, reaching titers of 40 mg/L in both cases. In all cases, Ter from Treponema denticola was the preferred trans-enoyl-CoA reductase. The titers of hexanoic acid and octanoic acid were further increased to almost 75 mg/L and 60 mg/L, respectively, when the pathway expression cassette was integrated into the genome and the fermentation was performed in a highly buffered YPD medium. We also co-expressed a butyryl-CoA pathway variant to increase the butyryl-CoA pool and support the chain extension. However, this mainly increased the titers of butyric acid and only slightly increased that of hexanoic acid. Finally, we also tested the deletion of two potential medium-chain acyl-CoA depleting reactions catalyzed by the thioesterase Tes1 and the medium-chain fatty acyl CoA synthase Faa2. However, their deletion did not affect the production titers. CONCLUSIONS By engineering the NADH metabolism and testing different reverse β-oxidation pathway variants, we extended the product spectrum and obtained the highest titers of octanoic acid and hexanoic acid reported in S. cerevisiae. Product toxicity and enzyme specificity must be addressed for the industrial application of the pathway in this organism.
Collapse
Affiliation(s)
- Fernando Garces Daza
- Faculty of Biological Sciences, Institute of Molecular Bioscience, Goethe-Universität Frankfurt Am Main, Max-von-Laue-Str.9, 60438, Frankfurt am Main, Germany
| | - Fabian Haitz
- Faculty of Biological Sciences, Institute of Molecular Bioscience, Goethe-Universität Frankfurt Am Main, Max-von-Laue-Str.9, 60438, Frankfurt am Main, Germany
| | - Alice Born
- Faculty of Biological Sciences, Institute of Molecular Bioscience, Goethe-Universität Frankfurt Am Main, Max-von-Laue-Str.9, 60438, Frankfurt am Main, Germany
| | - Eckhard Boles
- Faculty of Biological Sciences, Institute of Molecular Bioscience, Goethe-Universität Frankfurt Am Main, Max-von-Laue-Str.9, 60438, Frankfurt am Main, Germany.
| |
Collapse
|
24
|
Revealing the Characteristics of Glucose- and Lactate-Based Chain Elongation for Caproate Production by Caproicibacterium lactatifermentans through Transcriptomic, Bioenergetic, and Regulatory Analyses. mSystems 2022; 7:e0053422. [PMID: 36073803 PMCID: PMC9600882 DOI: 10.1128/msystems.00534-22] [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] [Indexed: 12/24/2022] Open
Abstract
Caproate, an important medium-chain fatty acid, can only be synthesized by limited bacterial species by using ethanol, lactate, or certain saccharides. Caproicibacterium lactatifermentans is a promising caproate producer due to its glucose and lactate utilization capabilities. However, the global cellular responses of this bacterium to different carbon sources were not well understood. Here, C. lactatifermentans showed robust growth on glucose but more active caproate synthesis on lactate. Comparative transcriptome revealed that the genes involved in reverse β-oxidation for caproate synthesis and V-type ATPase-dependent ATP generation were upregulated under lactate condition, while several genes responsible for biomass synthesis were upregulated under glucose condition. Based on metabolic pathway reconstructions and bioenergetics analysis, the biomass accumulation on glucose condition may be supported by sufficient supplies of ATP and metabolite intermediates via glycolysis. In contrast, the ATP yield per glucose equivalent from lactate conversion into caproate was only 20% of that from glucose. Thus, the upregulation of the reverse β-oxidation genes may be essential for cell survival under lactate conditions. Furthermore, the remarkably decreased lactate utilization was observed after glucose acclimatization, indicating the negative modulation of lactate utilization by glucose metabolism. Based on the cotranscription of the lactate utilization repressor gene lldR with sugar-specific PTS genes and the opposite expression patterns of lldR and lactate utilization genes, a novel regulatory mechanism of glucose-repressed lactate utilization mediated via lldR was proposed. The results of this study suggested the molecular mechanism underlying differential physiologic and metabolic characteristics of C. lactatifermentans grown on glucose and lactate. IMPORTANCE Caproicibacterium lactatifermentans is a unique and robust caproate-producing bacterium in the family Oscillospiraceae due to its lactate utilization capability, whereas its close relatives such as Caproicibacterium amylolyticum, Caproiciproducens galactitolivorans, and Caproicibacter fermentans cannot utilize lactate but produce lactate as the main fermentation end product. Moreover, C. lactatifermentans can also utilize several saccharides such as glucose and maltose. Although the metabolic versatility of the bacterium makes it to be a promising industrial caproate producer, the cellular responses of C. lactatifermentans to different carbon sources were unknown. Here, the molecular mechanisms of biomass synthesis supported by glucose utilization and the cell survival supported by lactate utilization were revealed. A novel insight into the regulatory machinery in which glucose negatively regulates lactate utilization was proposed. This study provides a valuable basis to control and optimize caproate production, which will contribute to achieving a circular economy and environmental sustainability.
Collapse
|