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Dickey RM, Gopal MR, Nain P, Kunjapur AM. Recent developments in enzymatic and microbial biosynthesis of flavor and fragrance molecules. J Biotechnol 2024; 389:43-60. [PMID: 38616038 DOI: 10.1016/j.jbiotec.2024.04.004] [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: 02/16/2024] [Revised: 04/08/2024] [Accepted: 04/08/2024] [Indexed: 04/16/2024]
Abstract
Flavors and fragrances are an important class of specialty chemicals for which interest in biomanufacturing has risen during recent years. These naturally occurring compounds are often amenable to biosynthesis using purified enzyme catalysts or metabolically engineered microbial cells in fermentation processes. In this review, we provide a brief overview of the categories of molecules that have received the greatest interest, both academically and industrially, by examining scholarly publications as well as patent literature. Overall, we seek to highlight innovations in the key reaction steps and microbial hosts used in flavor and fragrance manufacturing.
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Affiliation(s)
- Roman M Dickey
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19711, USA
| | - Madan R Gopal
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19711, USA
| | - Priyanka Nain
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19711, USA
| | - Aditya M Kunjapur
- Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19711, USA.
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2
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Guo X, Ding Y, Chen Y, Fu H, Wang J. Microbial cell factory for butyl butyrate production: Knowledges and perspectives. Microb Biotechnol 2024; 17:e14502. [PMID: 38888486 PMCID: PMC11184938 DOI: 10.1111/1751-7915.14502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2024] [Revised: 05/08/2024] [Accepted: 05/12/2024] [Indexed: 06/20/2024] Open
Abstract
Butyl butyrate is a short-chain fatty acid ester (C8) with a fruity aroma. It has broad prospects in the fields of foods, cosmetics and biofuels. At present, butyl butyrate is produced by chemical synthesis in the industry, but it is highly dependent on petroleum-based products. The growing concerns regarding the future scarcity of fossil fuels have been strongly promoted the transition from traditional fossil fuels and products to renewable bioenergy and biochemicals. Therefore, it is necessary to develop a green biochemical technology to replace traditional petroleum-based materials. In recent years, microorganisms such as Escherichia coli and Clostridium have been engineered to serve as cell factories for the sustainable one-pot production of short-chain fatty acid esters, including butyl butyrate. This opinion highlights the recent development in the use of lipases and alcohol acyltransferases (AATs) for butyl butyrate production in microbial fermentation, as well as future perspectives.
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Affiliation(s)
- Xiaolong Guo
- School of Biology and Biological EngineeringSouth China University of TechnologyGuangzhouChina
| | - Yuqing Ding
- School of Biology and Biological EngineeringSouth China University of TechnologyGuangzhouChina
| | - Yufan Chen
- School of Biology and Biological EngineeringSouth China University of TechnologyGuangzhouChina
| | - Hongxin Fu
- School of Biology and Biological EngineeringSouth China University of TechnologyGuangzhouChina
- Guangdong Provincial Key Laboratory of Fermentation and Enzyme EngineeringSouth China University of TechnologyGuangzhouChina
- State Key Laboratory of Pulp and Paper EngineeringSouth China University of TechnologyGuangzhouChina
| | - Jufang Wang
- School of Biology and Biological EngineeringSouth China University of TechnologyGuangzhouChina
- Guangdong Provincial Key Laboratory of Fermentation and Enzyme EngineeringSouth China University of TechnologyGuangzhouChina
- State Key Laboratory of Pulp and Paper EngineeringSouth China University of TechnologyGuangzhouChina
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3
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Seo H, Singh P, Wyman CE, Cai CM, Trinh CT. Rewiring metabolism of Clostridium thermocellum for consolidated bioprocessing of lignocellulosic biomass poplar to produce short-chain esters. BIORESOURCE TECHNOLOGY 2023:129263. [PMID: 37271458 DOI: 10.1016/j.biortech.2023.129263] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 05/29/2023] [Accepted: 05/30/2023] [Indexed: 06/06/2023]
Abstract
Consolidated bioprocessing (CBP) of lignocellulosic biomass uses cellulolytic microorganisms to enable enzyme production, saccharification, and fermentation to produce biofuels, biochemicals, and biomaterials in a single step. However, understanding and redirecting metabolisms of these microorganisms compatible with CBP are limited. Here, a cellulolytic thermophile Clostridium thermocellum was engineered and demonstrated to be compatible with CBP integrated with a Co-solvent Enhanced Lignocellulosic Fractionation (CELF) pretreatment for conversion of hardwood poplar into short-chain esters with industrial use as solvents, flavors, fragrances, and biofuels. The recombinant C. thermocellum engineered with deletion of carbohydrate esterases and stable overexpression of alcohol acetyltransferases improved ester production without compromised deacetylation activities. These esterases were discovered to exhibit promiscuous thioesterase activities and their deletion enhanced ester production by rerouting the electron and carbon metabolism. Ester production was further improved up to 80-fold and ester composition could be modulated by deleting lactate biosynthesis and using poplar with different pretreatment severity.
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Affiliation(s)
- Hyeongmin Seo
- Department of Chemical and Biomolecular Engineering, The University of Tennessee, Knoxville, TN, USA; Center of Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Priyanka Singh
- Center of Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, USA; Chemical and Environmental Engineering Department, University of California, Riverside, CA 92521, USA
| | - Charles E Wyman
- Center of Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, USA; Chemical and Environmental Engineering Department, University of California, Riverside, CA 92521, USA
| | - Charles M Cai
- Center of Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, USA; Chemical and Environmental Engineering Department, University of California, Riverside, CA 92521, USA
| | - Cong T Trinh
- Department of Chemical and Biomolecular Engineering, The University of Tennessee, Knoxville, TN, USA; Center of Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
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4
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Guo X, Zhang H, Feng J, Yang L, Luo K, Fu H, Wang J. De novo biosynthesis of butyl butyrate in engineered Clostridium tyrobutyricum. Metab Eng 2023; 77:64-75. [PMID: 36948242 DOI: 10.1016/j.ymben.2023.03.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 03/07/2023] [Accepted: 03/20/2023] [Indexed: 03/24/2023]
Abstract
Butyl butyrate has broad applications in foods, cosmetics, solvents, and biofuels. Microbial synthesis of bio-based butyl butyrate has been regarded as a promising approach recently. Herein, we engineered Clostridium tyrobutyricum ATCC 25755 to achieve de novo biosynthesis of butyl butyrate from fermentable sugars. Through introducing the butanol synthetic pathway (enzyme AdhE2), screening alcohol acyltransferases (AATs), adjusting transcription of VAAT and adhE2 (i.e., optimizing promoter), and efficient supplying butyryl-CoA, an excellent engineered strain, named MUV3, was obtained with ability to produce 4.58 g/L butyl butyrate at 25 °C with glucose in serum bottles. More NADH is needed for butyl butyrate synthesis, thus mannitol (the more reduced substrate) was employed to produce butyl butyrate. Ultimately, 62.59 g/L butyl butyrate with a selectivity of 95.97%, and a yield of 0.21 mol/mol was obtained under mannitol with fed-batch fermentation in a 5 L bioreactor, which is the highest butyl butyrate titer reported so far. Altogether, this study presents an anaerobic fermentative platform for de novo biosynthesis of butyl butyrate in one step, which lays the foundation for butyl butyrate biosynthesis from renewable biomass feedstocks.
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Affiliation(s)
- Xiaolong Guo
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, 510006, China
| | - Huihui Zhang
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, 510006, China
| | - Jun Feng
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, 510006, China
| | - Lu Yang
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, 510006, China
| | - Kui Luo
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, 510006, China
| | - Hongxin Fu
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, 510006, China; Guangdong Provincial Key Laboratory of Fermentation and Enzyme Engineering, South China University of Technology, Guangzhou, 510006, China.
| | - Jufang Wang
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, 510006, China; Guangdong Provincial Key Laboratory of Fermentation and Enzyme Engineering, South China University of Technology, Guangzhou, 510006, China.
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5
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Buchecker F, Baum A, Loos HM, Buettner A. Follow your nose - Traveling the world of odorants in new cars. INDOOR AIR 2022; 32:e13014. [PMID: 35347790 DOI: 10.1111/ina.13014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 02/21/2022] [Accepted: 02/25/2022] [Indexed: 06/14/2023]
Abstract
Volatile organic compounds of the vehicle interior are well investigated, but only limited information is available on the odorants of the passenger cabin. To close this gap, we aimed at specifically elucidating the odor, as a general proof of principle, of two new cars with different seat upholstery in a controlled environment using a targeted odorant analysis. In a first step, odor profiles were evaluated by a descriptive sensory analysis. Then, potent odorants of the passenger cabins were characterized by gas chromatography-olfactometry and ranked according to their odor potency via odor extract dilution analysis. Using this approach, 41 potent odorants were detected, and 39 odorants were successfully identified by two-dimensional gas chromatography-mass spectrometry/olfactometry. In a third step, important odorants of the vehicle interior were quantified by means of internal standard addition. The most dominant odorants could be assigned to several specific substance classes comprising esters, saturated and unsaturated aldehydes, unsaturated ketones, rose ketones, phenolic and benzene derivatives, and pyrazines, occurring in a concentration range between 0.05 and 219 ng/L in air. Of these potent odorants, the aldehydes 2-butylhept-2-enal, 2-propyloct-2-enal, and (Z)-2-butyloct-2-enal are reported here for the first time as odorants in the environment of a passenger cabin.
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Affiliation(s)
- Florian Buchecker
- Department of Chemistry and Pharmacy, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
- BMW Group, Munich, Germany
| | - Adina Baum
- Department of Chemistry and Pharmacy, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Helene M Loos
- Department of Chemistry and Pharmacy, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
- Fraunhofer Institute for Process Engineering and Packaging IVV, Freising, Germany
| | - Andrea Buettner
- Department of Chemistry and Pharmacy, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
- Fraunhofer Institute for Process Engineering and Packaging IVV, Freising, Germany
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Wang Q, Al Makishah NH, Li Q, Li Y, Liu W, Sun X, Wen Z, Yang S. Developing Clostridia as Cell Factories for Short- and Medium-Chain Ester Production. Front Bioeng Biotechnol 2021; 9:661694. [PMID: 34164382 PMCID: PMC8215697 DOI: 10.3389/fbioe.2021.661694] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Accepted: 04/19/2021] [Indexed: 11/21/2022] Open
Abstract
Short- and medium-chain volatile esters with flavors and fruity fragrances, such as ethyl acetate, butyl acetate, and butyl butyrate, are usually value-added in brewing, food, and pharmacy. The esters can be naturally produced by some microorganisms. As ester-forming reactions are increasingly deeply understood, it is possible to produce esters in non-natural but more potential hosts. Clostridia are a group of important industrial microorganisms since they can produce a variety of volatile organic acids and alcohols with high titers, especially butanol and butyric acid through the CoA-dependent carbon chain elongation pathway. This implies sufficient supplies of acyl-CoA, organic acids, and alcohols in cells, which are precursors for ester production. Besides, some Clostridia could utilize lignocellulosic biomass, industrial off-gas, or crude glycerol to produce other branched or straight-chain alcohols and acids. Therefore, Clostridia offer great potential to be engineered to produce short- and medium-chain volatile esters. In the review, the efforts to produce esters from Clostridia via in vitro lipase-mediated catalysis and in vivo alcohol acyltransferase (AAT)-mediated reaction are comprehensively revisited. Besides, the advantageous characteristics of several Clostridia and clostridial consortia for bio-ester production and the driving force of synthetic biology to clostridial chassis development are also discussed. It is believed that synthetic biotechnology should enable the future development of more effective Clostridia for ester production.
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Affiliation(s)
- Qingzhuo Wang
- School of Food Science and Pharmaceutical Engineering, Nanjing Normal University, Nanjing, China
| | - Naief H Al Makishah
- Department of Environmental Sciences, Faculty of Meteorology, Environment and Arid Land Agriculture, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Qi Li
- College of Life Sciences, Sichuan Normal University, Chengdu, China
| | - Yanan Li
- School of Food Science and Pharmaceutical Engineering, Nanjing Normal University, Nanjing, China
| | - Wenzheng Liu
- School of Food Science and Pharmaceutical Engineering, Nanjing Normal University, Nanjing, China
| | - Xiaoman Sun
- School of Food Science and Pharmaceutical Engineering, Nanjing Normal University, Nanjing, China
| | - Zhiqiang Wen
- School of Food Science and Pharmaceutical Engineering, Nanjing Normal University, Nanjing, China
| | - Sheng Yang
- Huzhou Center of Industrial Biotechnology, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai, China.,Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China
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Seo H, Lee JW, Giannone RJ, Dunlap NJ, Trinh CT. Engineering promiscuity of chloramphenicol acetyltransferase for microbial designer ester biosynthesis. Metab Eng 2021; 66:179-190. [PMID: 33872779 DOI: 10.1016/j.ymben.2021.04.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Revised: 04/06/2021] [Accepted: 04/11/2021] [Indexed: 02/07/2023]
Abstract
Robust and efficient enzymes are essential modules for metabolic engineering and synthetic biology strategies across biological systems to engineer whole-cell biocatalysts. By condensing an acyl-CoA and an alcohol, alcohol acyltransferases (AATs) can serve as interchangeable metabolic modules for microbial biosynthesis of a diverse class of ester molecules with broad applications as flavors, fragrances, solvents, and drop-in biofuels. However, the current lack of robust and efficient AATs significantly limits their compatibility with heterologous precursor pathways and microbial hosts. Through bioprospecting and rational protein engineering, we identified and engineered promiscuity of chloramphenicol acetyltransferases (CATs) from mesophilic prokaryotes to function as robust and efficient AATs compatible with at least 21 alcohol and 8 acyl-CoA substrates for microbial biosynthesis of linear, branched, saturated, unsaturated and/or aromatic esters. By plugging the best engineered CAT (CATec3 Y20F) into the gram-negative mesophilic bacterium Escherichia coli, we demonstrated that the recombinant strain could effectively convert various alcohols into desirable esters, for instance, achieving a titer of 13.9 g/L isoamyl acetate with 95% conversion by fed-batch fermentation. The recombinant E. coli was also capable of simulating the ester profile of roses with high conversion (>97%) and titer (>1 g/L) from fermentable sugars at 37 °C. Likewise, a recombinant gram-positive, cellulolytic, thermophilic bacterium Clostridium thermocellum harboring CATec3 Y20F could produce many of these esters from recalcitrant cellulosic biomass at elevated temperatures (>50 °C) due to the engineered enzyme's remarkable thermostability. Overall, the engineered CATs can serve as a robust and efficient platform for designer ester biosynthesis from renewable and sustainable feedstocks.
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Affiliation(s)
- Hyeongmin Seo
- Department of Chemical and Biomolecular Engineering, The University of Tennessee, Knoxville, TN, USA; Center of Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Jong-Won Lee
- Bredesen Center for Interdisciplinary Research and Graduate Education, The University of Tennessee, Knoxville, TN, USA; Center of Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Richard J Giannone
- Center of Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, USA; Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Noah J Dunlap
- Department of Chemical and Biomolecular Engineering, The University of Tennessee, Knoxville, TN, USA
| | - Cong T Trinh
- Department of Chemical and Biomolecular Engineering, The University of Tennessee, Knoxville, TN, USA; Bredesen Center for Interdisciplinary Research and Graduate Education, The University of Tennessee, Knoxville, TN, USA; Center of Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
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8
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Sun L, Xin F, Alper HS. Bio-synthesis of food additives and colorants-a growing trend in future food. Biotechnol Adv 2021; 47:107694. [PMID: 33388370 DOI: 10.1016/j.biotechadv.2020.107694] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 12/24/2020] [Accepted: 12/27/2020] [Indexed: 02/07/2023]
Abstract
Food additives and colorants are extensively used in the food industry to improve food quality and safety during processing, storage and packing. Sourcing of these molecules is predominately through three means: extraction from natural sources, chemical synthesis, and bio-production, with the first two being the most utilized. However, growing demands for sustainability, safety and "natural" products have renewed interest in using bio-based production methods. Likewise, the move to more cultured foods and meat alternatives requires the production of new additives and colorants. The production of bio-based food additives and colorants is an interdisciplinary research endeavor and represents a growing trend in future food. To highlight the potential of microbial hosts for food additive and colorant production, we focus on current advances for example molecules based on their utilization stage and bio-production yield as follows: (I) approved and industrially produced with high titers; (II) approved and produced with decent titers (in the g/L range), but requiring further engineering to reduce production costs; (III) approved and produced with very early stage titers (in the mg/L range); and (IV) new/potential candidates that have not been approved but can be sourced through microbes. Promising approaches, as well as current challenges and future directions will also be thoroughly discussed for the bioproduction of these food additives and colorants.
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Affiliation(s)
- Lichao Sun
- Institute of Food Science and Technology, Chinese Academy of Agricultural Sciences, Beijing 100193, People's Republic of China.
| | - Fengjiao Xin
- Institute of Food Science and Technology, Chinese Academy of Agricultural Sciences, Beijing 100193, People's Republic of China.
| | - Hal S Alper
- Institute for Cellular and Molecular Biology, The University of Texas at Austin, 2500 Speedway Avenue, Austin, TX 78712, United States; McKetta Department of Chemical Engineering, The University of Texas at Austin, 200 E Dean Keeton St. Stop C0400, Austin, TX 78712, United States.
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9
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Garcia S, Thompson RA, Giannone RJ, Dash S, Maranas CD, Trinh CT. Development of a Genome-Scale Metabolic Model of Clostridium thermocellum and Its Applications for Integration of Multi-Omics Datasets and Computational Strain Design. Front Bioeng Biotechnol 2020; 8:772. [PMID: 32974289 PMCID: PMC7471609 DOI: 10.3389/fbioe.2020.00772] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Accepted: 06/18/2020] [Indexed: 01/29/2023] Open
Abstract
Solving environmental and social challenges such as climate change requires a shift from our current non-renewable manufacturing model to a sustainable bioeconomy. To lower carbon emissions in the production of fuels and chemicals, plant biomass feedstocks can replace petroleum using microorganisms as biocatalysts. The anaerobic thermophile Clostridium thermocellum is a promising bacterium for bioconversion due to its capability to efficiently degrade lignocellulosic biomass. However, the complex metabolism of C. thermocellum is not fully understood, hindering metabolic engineering to achieve high titers, rates, and yields of targeted molecules. In this study, we developed an updated genome-scale metabolic model of C. thermocellum that accounts for recent metabolic findings, has improved prediction accuracy, and is standard-conformant to ensure easy reproducibility. We illustrated two applications of the developed model. We first formulated a multi-omics integration protocol and used it to understand redox metabolism and potential bottlenecks in biofuel (e.g., ethanol) production in C. thermocellum. Second, we used the metabolic model to design modular cells for efficient production of alcohols and esters with broad applications as flavors, fragrances, solvents, and fuels. The proposed designs not only feature intuitive push-and-pull metabolic engineering strategies, but also present novel manipulations around important central metabolic branch-points. We anticipate the developed genome-scale metabolic model will provide a useful tool for system analysis of C. thermocellum metabolism to fundamentally understand its physiology and guide metabolic engineering strategies to rapidly generate modular production strains for effective biosynthesis of biofuels and biochemicals from lignocellulosic biomass.
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Affiliation(s)
- Sergio Garcia
- Department of Chemical and Biomolecular Engineering, The University of Tennessee, Knoxville, TN, United States.,Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, United States
| | - R Adam Thompson
- Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, United States.,Bredesen Center for Interdisciplinary Research and Graduate Education, The University of Tennessee, Knoxville, TN, United States.,Oak Ridge National Laboratory, Oak Ridge, TN, United States
| | - Richard J Giannone
- Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, United States.,Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, United States
| | - Satyakam Dash
- Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, United States.,Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, United States
| | - Costas D Maranas
- Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, United States.,Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, United States
| | - Cong T Trinh
- Department of Chemical and Biomolecular Engineering, The University of Tennessee, Knoxville, TN, United States.,Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, United States.,Bredesen Center for Interdisciplinary Research and Graduate Education, The University of Tennessee, Knoxville, TN, United States.,Oak Ridge National Laboratory, Oak Ridge, TN, United States
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Mazzoli R, Olson D. Clostridium thermocellum: A microbial platform for high-value chemical production from lignocellulose. ADVANCES IN APPLIED MICROBIOLOGY 2020; 113:111-161. [PMID: 32948265 DOI: 10.1016/bs.aambs.2020.07.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Second generation biorefining, namely fermentation processes based on lignocellulosic feedstocks, has attracted tremendous interest (owing to the large availability and low cost of this biomass) as a strategy to produce biofuels and commodity chemicals that is an alternative to oil refining. However, the innate recalcitrance of lignocellulose has slowed progress toward economically viable processes. Consolidated bioprocessing (CBP), i.e., single-step fermentation of lignocellulose may dramatically reduce the current costs of 2nd generation biorefining. Metabolic engineering has been used as a tool to develop improved microbial strains supporting CBP. Clostridium thermocellum is among the most efficient cellulose degraders isolated so far and one of the most promising host organisms for application of CBP. The development of efficient and reliable genetic tools has allowed significant progress in metabolic engineering of this strain aimed at expanding the panel of growth substrates and improving the production of a number of commodity chemicals of industrial interest such as ethanol, butanol, isobutanol, isobutyl acetate and lactic acid. The present review aims to summarize recent developments in metabolic engineering of this organism which currently represents a reference model for the development of biocatalysts for 2nd generation biorefining.
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