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Wang H, Li H, Lee CK, Mat Nanyan NS, Tay GS. A systematic review on utilization of biodiesel-derived crude glycerol in sustainable polymers preparation. Int J Biol Macromol 2024; 261:129536. [PMID: 38278390 DOI: 10.1016/j.ijbiomac.2024.129536] [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: 11/20/2023] [Revised: 01/08/2024] [Accepted: 01/14/2024] [Indexed: 01/28/2024]
Abstract
With the rapid development of biodiesel, biodiesel-derived glycerol has become a promising renewable bioresource. The key to utilizing this bioresource lies in the value-added conversion of crude glycerol. While purifying crude glycerol into a pure form allows for diverse applications, the intricate nature of this process renders it costly and environmentally stressful. Consequently, technology facilitating the direct utilization of unpurified crude glycerol holds significant importance. It has been reported that crude glycerol can be bio-transformed or chemically converted into high-value polymers. These technologies provide cost-effective alternatives for polymer production while contributing to a more sustainable biodiesel industry. This review article describes the global production and quality characteristics of biodiesel-derived glycerol and investigates the influencing factors and treatment of the composition of crude glycerol including water, methanol, soap, matter organic non-glycerol, and ash. Additionally, this review also focused on the advantages and challenges of various technologies for converting crude glycerol into polymers, considering factors such as the compatibility of crude glycerol and the control of unfavorable factors. Lastly, the application prospect and value of crude glycerol conversion were discussed from the aspects of economy and environmental protection. The development of new technologies for the increased use of crude glycerol as a renewable feedstock for polymer production will be facilitated by the findings of this review, while promoting mass market applications.
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Affiliation(s)
- Hong Wang
- Bioresource Technology Division, School of Industrial Technology, Universiti Sains Malaysia, Penang USM 11800, Malaysia
| | - Hongpeng Li
- Tangshan Jinlihai Biodiesel Co. Ltd., 063000 Tangshan, China
| | - Chee Keong Lee
- Bioprocess Technology Division, School of Industrial Technology, Universiti Sains Malaysia, Penang USM 11800, Malaysia; School of Industrial Technology, Universiti Sains Malaysia, Penang USM 11800, Malaysia
| | - Noreen Suliani Mat Nanyan
- Bioprocess Technology Division, School of Industrial Technology, Universiti Sains Malaysia, Penang USM 11800, Malaysia; School of Industrial Technology, Universiti Sains Malaysia, Penang USM 11800, Malaysia
| | - Guan Seng Tay
- Bioresource Technology Division, School of Industrial Technology, Universiti Sains Malaysia, Penang USM 11800, Malaysia; Green Biopolymer, Coatings & Packaging Cluster, School of Industrial Technology, Universiti Sains Malaysia, Penang USM 11800, Malaysia.
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2
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Le HTQ, Lee EY. Insights into C1 and C3 assimilation pathways in type I methanotrophic bacterium from co-production of 1,2-propanediol and lactate. BIORESOURCE TECHNOLOGY 2022; 365:128172. [PMID: 36279980 DOI: 10.1016/j.biortech.2022.128172] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 10/15/2022] [Accepted: 10/17/2022] [Indexed: 06/16/2023]
Abstract
Methanotrophic bacteria are attractive hosts for mining metabolic pathways of C1 assimilation to produce value-added products. Herein, the type I methanotroph Methylotuvimicrobium alcaliphilum 20Z was employed to explore the carbon flux from methane and methanol via the EMP pathway to produce 1,2-propanediol (1,2-PDO). The production of 1,2-PDO on methane was found to be mainly restricted by the lower carbon flux toward the EMP pathway. The co-utilization of C1 substrates and glycerol (C3) could contribute to enhance 1,2-PDO. Lactate was co-produced in much higher amounts than 1,2-PDO. This unexpected product was probably derived from lactaldehyde by inherent aldehyde dehydrogenases. The 1,2-PDO production without increased accumulation of lactate was observed via establishing the acetol-based pathway by propane utilization with the overexpression of pmoD. This is the first study to provide experimental insights into the operation of metabolic routes for 1,2-PDO and lactate co-production from C1 and C3 compounds in methanotrophs.
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Affiliation(s)
- Hoa Thi Quynh Le
- Department of Chemical Engineering (BK21 FOUR Integrated Engineering Program), Kyung Hee University, Yongin 17104, Republic of Korea
| | - Eun Yeol Lee
- Department of Chemical Engineering (BK21 FOUR Integrated Engineering Program), Kyung Hee University, Yongin 17104, Republic of Korea.
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3
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Rational Metabolic Engineering Combined with Biosensor-Mediated Adaptive Laboratory Evolution for l-Cysteine Overproduction from Glycerol in Escherichia coli. FERMENTATION-BASEL 2022. [DOI: 10.3390/fermentation8070299] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
l-Cysteine is an important sulfur-containing amino acid with numerous applications in the pharmaceutical and cosmetic industries. The microbial production of l-cysteine has received substantial attention, and the supply of the precursor l-serine is important in l-cysteine biosynthesis. In this study, to achieve l-cysteine overproduction, we first increased l-serine production by deleting genes involved in the pathway of l-serine degradation to glycine (serine hydroxymethyl transferase, SHMT, encoded by glyA genes) in strain 4W (with l-serine titer of 1.1 g/L), thus resulting in strain 4WG with l-serine titer of 2.01 g/L. Second, the serine-biosensor based on the transcriptional regulator NCgl0581 of C. glutamicum was constructed in E. coli, and the validity and sensitivity of the biosensor were demonstrated in E. coli. Then 4WG was further evolved through adaptive laboratory evolution (ALE) combined with serine-biosensor, thus yielding the strain 4WGX with 4.13 g/L l-serine production. Moreover, the whole genome of the evolved strain 4WGX was sequenced, and ten non-synonymous mutations were found in the genome of strain 4WGX compared with strain 4W. Finally, 4WGX was used as the starting strain, and deletion of the l-cysteine desulfhydrases (encoded by tnaA), overexpression of serine acetyltransferase (encoded by cysE) and the key enzyme of transport pathway (encoded by ydeD) were performed in strain 4WGX. The recombinant strain 4WGX-∆tnaA-cysE-ydeD can produce 313.4 mg/L of l-cysteine using glycerol as the carbon source. This work provides an efficient method for the biosynthesis of value-added commodity products associated with glycerol conversion.
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4
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Engineered Microbial Cell Factories for Sustainable Production of L-Lactic Acid: A Critical Review. FERMENTATION-BASEL 2022. [DOI: 10.3390/fermentation8060279] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
With the increasing demand for the biodegradable polymer material polylactic acid and its advantage of being metabolized by the human body, L-lactic acid (L-LA) is becoming increasingly attractive in environmental protection and food industry applications. However, the supply of L-LA is not satisfied, and the price is still high. Compared to enzymatic and chemical synthesis methods, L-LA production by microbial fermentation has the advantages of low cost, large yield, simple operation, and environmental protection. This review summarizes the advances in engineering microbial cell factories to produce L-LA. First, the synthetic pathways and microorganisms for L-LA production are outlined. Then, the metabolic engineering strategies for constructing cell factories to overproduce L-LA are summarized and fermentation modes for L-LA production are also given. Finally, the challenges and prospects of the microbial production of L-LA are discussed. This review provides theoretical guidance for researchers engaged in L-LA production.
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5
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Kim K, Hou CY, Choe D, Kang M, Cho S, Sung BH, Lee DH, Lee SG, Kang TJ, Cho BK. Adaptive laboratory evolution of Escherichia coli W enhances gamma-aminobutyric acid production using glycerol as the carbon source. Metab Eng 2021; 69:59-72. [PMID: 34775076 DOI: 10.1016/j.ymben.2021.11.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 10/19/2021] [Accepted: 11/06/2021] [Indexed: 11/25/2022]
Abstract
The microbial conversion of glycerol into value-added commodity products has emerged as an attractive means to meet the demands of biosustainability. However, glycerol is a non-preferential carbon source for productive fermentation because of its low energy density. We employed evolutionary and metabolic engineering in tandem to construct an Escherichia coli strain with improved GABA production using glycerol as the feedstock carbon. Adaptive evolution of E. coli W under glycerol-limited conditions for 1300 generations harnessed an adapted strain with a metabolic system optimized for glycerol utilization. Mutation profiling, enzyme kinetic assays, and transcriptome analysis of the adapted strain allowed us to decipher the basis of glycerol adaptation at the molecular level. Importantly, increased substrate influx mediated by the mutant glpK and modulation of intracellular cAMP levels were the key drivers of improved fitness in the glycerol-limited condition. Leveraging the enhanced capability of glycerol utilization in the strain, we constructed a GABA-producing E. coli W-derivative with superior GABA production compared to the wild-type. Furthermore, rationally designed inactivation of the non-essential metabolic genes, including ackA, mgsA, and gabT, in the glycerol-adapted strain improved the final GABA titer and specific productivity by 3.9- and 4.3-fold, respectively, compared with the wild-type.
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Affiliation(s)
- Kangsan Kim
- Department of Biological Sciences and KI for the BioCentury, Korea Advanced Institute of Science and Technology, Daejeon, 34141, Republic of Korea
| | - Chen Yuan Hou
- Department of Chemical and Biochemical Engineering, Dongguk University-Seoul, Seoul, 04620, Republic of Korea
| | - Donghui Choe
- Department of Biological Sciences and KI for the BioCentury, Korea Advanced Institute of Science and Technology, Daejeon, 34141, Republic of Korea
| | - Minjeong Kang
- Department of Biological Sciences and KI for the BioCentury, Korea Advanced Institute of Science and Technology, Daejeon, 34141, Republic of Korea
| | - Suhyung Cho
- Department of Biological Sciences and KI for the BioCentury, Korea Advanced Institute of Science and Technology, Daejeon, 34141, Republic of Korea
| | - Bong Hyun Sung
- Synthetic Biology & Bioengineering Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, 34141, Republic of Korea
| | - Dae-Hee Lee
- Synthetic Biology & Bioengineering Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, 34141, Republic of Korea
| | - Seung-Goo Lee
- Synthetic Biology & Bioengineering Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, 34141, Republic of Korea
| | - Taek Jin Kang
- Department of Chemical and Biochemical Engineering, Dongguk University-Seoul, Seoul, 04620, Republic of Korea.
| | - Byung-Kwan Cho
- Department of Biological Sciences and KI for the BioCentury, Korea Advanced Institute of Science and Technology, Daejeon, 34141, Republic of Korea.
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Lad BC, Coleman SM, Alper HS. Microbial valorization of underutilized and nonconventional waste streams. J Ind Microbiol Biotechnol 2021; 49:6371101. [PMID: 34529075 PMCID: PMC9118980 DOI: 10.1093/jimb/kuab056] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Accepted: 09/14/2021] [Indexed: 12/12/2022]
Abstract
The growing burden of waste disposal coupled with natural resource scarcity has renewed interest in the remediation, valorization, and/or repurposing of waste. Traditional approaches such as composting, anaerobic digestion, use in fertilizers or animal feed, or incineration for energy production extract very little value out of these waste streams. In contrast, waste valorization into fuels and other biochemicals via microbial fermentation is an area of growing interest. In this review, we discuss microbial valorization of nonconventional, aqueous waste streams such as food processing effluents, wastewater streams, and other industrial wastes. We categorize these waste streams as carbohydrate-rich food wastes, lipid-rich wastes, and other industrial wastes. Recent advances in microbial valorization of these nonconventional waste streams are highlighted, along with a discussion of the specific challenges and opportunities associated with impurities, nitrogen content, toxicity, and low productivity.
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Affiliation(s)
- Beena C Lad
- Department of Molecular Biosciences, The University of Texas at Austin, 100 East 24th Street Stop A5000, Austin, TX 78712 USA
| | - Sarah M Coleman
- McKetta Department of Chemical Engineering, The University of Texas at Austin, 200 E Dean Keeton St. Stop C0400, Austin, TX 78712 USA
| | - Hal S Alper
- McKetta Department of Chemical Engineering, The University of Texas at Austin, 200 E Dean Keeton St. Stop C0400, Austin, TX 78712 USA.,Institute for Cellular and Molecular Biology, The University of Texas at Austin, 2500 Speedway Avenue, Austin, Texas 78712 USA
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Augustiniene E, Valanciene E, Matulis P, Syrpas M, Jonuskiene I, Malys N. Bioproduction of l- and d-lactic acids: advances and trends in microbial strain application and engineering. Crit Rev Biotechnol 2021; 42:342-360. [PMID: 34412525 DOI: 10.1080/07388551.2021.1940088] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Lactic acid is an important platform chemical used in the food, agriculture, cosmetic, pharmaceutical, and chemical industries. It serves as a building block for the production of polylactic acid (PLA), a biodegradable polymer, which can replace traditional petroleum-based plastics and help to reduce environmental pollution. Cost-effective production of optically pure l- and d-lactic acids is necessary to achieve a quality and thermostable PLA product. This paper evaluates research advances in the bioproduction of l- and d-lactic acids using microbial fermentation. Special emphasis is given to the development of metabolically engineered microbial strains and processes tailored to alternative and flexible feedstock concepts such as: lignocellulose, glycerol, C1-gases, and agricultural-food industry byproducts. Alternative fermentation concepts that can improve lactic acid production are discussed. The potential use of inducible gene expression systems for the development of biosensors to facilitate the screening and engineering of lactic acid-producing microorganisms is discussed.
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Affiliation(s)
- Ernesta Augustiniene
- Faculty of Chemical Technology, Bioprocess Research Centre, Kaunas University of Technology, Kaunas, Lithuania
| | - Egle Valanciene
- Faculty of Chemical Technology, Bioprocess Research Centre, Kaunas University of Technology, Kaunas, Lithuania
| | - Paulius Matulis
- Faculty of Chemical Technology, Bioprocess Research Centre, Kaunas University of Technology, Kaunas, Lithuania
| | - Michail Syrpas
- Faculty of Chemical Technology, Bioprocess Research Centre, Kaunas University of Technology, Kaunas, Lithuania
| | - Ilona Jonuskiene
- Faculty of Chemical Technology, Bioprocess Research Centre, Kaunas University of Technology, Kaunas, Lithuania
| | - Naglis Malys
- Faculty of Chemical Technology, Bioprocess Research Centre, Kaunas University of Technology, Kaunas, Lithuania
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8
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A Focus on the Transformation Processes for the Valorization of Glycerol Derived from the Production Cycle of Biofuels. Catalysts 2021. [DOI: 10.3390/catal11020280] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Glycerol is a valuable by-product in the biodiesel industries. However, the increase in biodiesel production resulted in an excess production of glycerol, with a limited market compared to its availability. Precisely because glycerol became a waste to be disposed of, the costs of biodiesel production have reduced. From an environmental point of view, identifying reactions that can convert glycerol into new products that can be reused in different applications has become a real necessity. According to the unique structural characteristics of glycerol, transformation processes can lead to different chemical functionalities through redox reactions, dehydration, esterification, and etherification, with the formation of products that can be applied both at the finest chemical level and to bulk chemistry.
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9
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Abstract
Energy policies in the US and in the EU during the last decades have been focused on enhanced oil and gas recovery, including the so-called tertiary extraction or enhanced oil recovery (EOR), on one hand, and the development and implementation of renewable energy vectors, on the other, including biofuels as bioethanol (mainly in US and Brazil) and biodiesel (mainly in the EU) [...]
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10
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Abedi E, Hashemi SMB. Lactic acid production - producing microorganisms and substrates sources-state of art. Heliyon 2020; 6:e04974. [PMID: 33088933 PMCID: PMC7566098 DOI: 10.1016/j.heliyon.2020.e04974] [Citation(s) in RCA: 104] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 06/08/2020] [Accepted: 09/16/2020] [Indexed: 01/18/2023] Open
Abstract
Lactic acid is an organic compound produced via fermentation by different microorganisms that are able to use different carbohydrate sources. Lactic acid bacteria are the main bacteria used to produce lactic acid and among these, Lactobacillus spp. have been showing interesting fermentation capacities. The use of Bacillus spp. revealed good possibilities to reduce the fermentative costs. Interestingly, lactic acid high productivity was achieved by Corynebacterium glutamicum and E. coli, mainly after engineering genetic modification. Fungi, like Rhizopus spp. can metabolize different renewable carbon resources, with advantageously amylolytic properties to produce lactic acid. Additionally, yeasts can tolerate environmental restrictions (for example acidic conditions), being the wild-type low lactic acid producers that have been improved by genetic manipulation. Microalgae and cyanobacteria, as photosynthetic microorganisms can be an alternative lactic acid producer without carbohydrate feed costs. For lactic acid production, it is necessary to have substrates in the fermentation medium. Different carbohydrate sources can be used, from plant waste as molasses, starchy, lignocellulosic materials as agricultural and forestry residues. Dairy waste also can be used by the addition of supplementary components with a nitrogen source.
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Affiliation(s)
- Elahe Abedi
- Department of Food Science and Technology, College of Agriculture, Fasa University, Fasa, Iran
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11
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Zhan T, Chen Q, Zhang C, Bi C, Zhang X. Constructing a Novel Biosynthetic Pathway for the Production of Glycolate from Glycerol in Escherichia coli. ACS Synth Biol 2020; 9:2600-2609. [PMID: 32794740 DOI: 10.1021/acssynbio.0c00404] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Glycolate is an important α-hydroxy acid with a wide range of industrial applications. The current industrial production of glycolate mainly depends on chemical synthesis, but biochemical production from renewable resources using engineered microorganisms is increasingly viewed as an attractive alternative. Crude glycerol is an abundant byproduct of biodiesel production and a widely investigated potential sustainable feedstock. Here, we constructed a novel biosynthetic pathway for the production of glycolate from glycerol in Escherichia coli. The pathway starts from the oxidation of glycerol to d-glycerate by alditol oxidase, followed by sequential enzymatic dehydrogenation and decarboxylation as well as reduction reactions. We screened and characterized the catalytic activity of candidate enzymes, and a variant of alditol oxidase from Streptomyces coelicolor A3(2), 2-hydroxyglutarate-pyruvate transhydrogenase from Saccharomyces cerevisiae, α-ketoisovalerate decarboxylase from Lactococcus lactis, and aldehyde dehydrogenase from Escherichia coli were selected and assembled to create an artificial operon for the biosynthetic production of glycolate from glycerol. We also characterized the native strong constitutive promoter Plpp from E. coli and compared it with the PT7 promoter, which was employed to express the artificial operon on the plasmid pSC105-ADKA. To redirect glycerol flux toward glycolate synthesis, we deleted key genes of the native glycerol assimilation pathways and other branches of native E. coli metabolism, and we introduced a second plasmid expressing Dld3 to reduce the accumulation of the intermediate d-glycerate. Finally, the engineered strain TZ-108 harboring pSC105-ADKA and pACYC184-Plpp-Dld3 produced 0.64 g/L glycolate in shake flasks, which was increased to 4.74 g/L in fed-batch fermentation. This study provides an alternative pathway for glycolate synthesis and demonstrates the potential for producing other commodity chemicals by redesigning glycerol metabolism.
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Affiliation(s)
- Tao Zhan
- Key Laboratory of Systems Microbial Biotechnology, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China
| | - Qian Chen
- Key Laboratory of Systems Microbial Biotechnology, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China
| | - Chao Zhang
- College of Chemistry and Life Sciences, Changchun University of Technology, Changchun, Jilin 130012, China
| | - Changhao Bi
- Key Laboratory of Systems Microbial Biotechnology, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China
| | - Xueli Zhang
- Key Laboratory of Systems Microbial Biotechnology, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China
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12
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Liu EJ, Tseng IT, Chen YL, Pang JJ, Shen ZX, Li SY. The Physiological Responses of Escherichia coli Triggered by Phosphoribulokinase (PrkA) and Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase (Rubisco). Microorganisms 2020; 8:microorganisms8081187. [PMID: 32759862 PMCID: PMC7463662 DOI: 10.3390/microorganisms8081187] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 07/24/2020] [Accepted: 07/24/2020] [Indexed: 11/20/2022] Open
Abstract
Phosphoribulokinase (PrkA) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) have been proposed to create a heterologous Rubisco-based engineered pathway in Escherichia coli for in situ CO2 recycling. While the feasibility of a Rubisco-based engineered pathway has been shown, heterologous expressions of PrkA and Rubisco also induced physiological responses in E. coli that may compete with CO2 recycling. In this study, the metabolic shifts caused by PrkA and Rubisco were investigated in recombinant strains where ppc and pta genes (encodes phosphoenolpyruvate carboxylase and phosphate acetyltransferase, respectively) were deleted from E. coli MZLF (E. coli BL21(DE3) Δzwf, ΔldhA, Δfrd). It has been shown that the demand for ATP created by the expression of PrkA significantly enhanced the glucose consumptions of E. coli CC (MZLF Δppc) and E. coli CA (MZLF Δppc, Δpta). The accompanying metabolic shift is suggested to be the mgsA route (the methylglyoxal pathway) which results in the lactate production for reaching the redox balance. The overexpression of Rubisco not only enhanced glucose consumption but also bacterial growth. Instead of the mgsA route, the overproduction of the reducing power was balanced by the ethanol production. It is suggested that Rubisco induces a high demand for acetyl-CoA which is subsequently used by the glyoxylate shunt. Therefore, Rubisco can enhance bacterial growth. This study suggests that responses induced by the expression of PrkA and Rubisco will reach a new energy balance profile inside the cell. The new profile results in a new distribution of the carbon flow and thus carbons cannot be majorly directed to the Rubisco-based engineered pathway.
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Affiliation(s)
- En-Jung Liu
- Department of Chemical Engineering, National Chung Hsing University, Taichung City 40227, Taiwan.; (E.-J.L.); (I.-T.T.); (Y.-L.C.); (J.-J.P.); (Z.-X.S.)
| | - I-Ting Tseng
- Department of Chemical Engineering, National Chung Hsing University, Taichung City 40227, Taiwan.; (E.-J.L.); (I.-T.T.); (Y.-L.C.); (J.-J.P.); (Z.-X.S.)
| | - Yi-Ling Chen
- Department of Chemical Engineering, National Chung Hsing University, Taichung City 40227, Taiwan.; (E.-J.L.); (I.-T.T.); (Y.-L.C.); (J.-J.P.); (Z.-X.S.)
| | - Ju-Jiun Pang
- Department of Chemical Engineering, National Chung Hsing University, Taichung City 40227, Taiwan.; (E.-J.L.); (I.-T.T.); (Y.-L.C.); (J.-J.P.); (Z.-X.S.)
| | - Zhi-Xuan Shen
- Department of Chemical Engineering, National Chung Hsing University, Taichung City 40227, Taiwan.; (E.-J.L.); (I.-T.T.); (Y.-L.C.); (J.-J.P.); (Z.-X.S.)
| | - Si-Yu Li
- Department of Chemical Engineering, National Chung Hsing University, Taichung City 40227, Taiwan.; (E.-J.L.); (I.-T.T.); (Y.-L.C.); (J.-J.P.); (Z.-X.S.)
- Innovation and Development Center of Sustainable Agriculture, National Chung Hsing University, Taichung City 40227, Taiwan
- Correspondence: ; Tel.: +886-4-2284-0510 (ext. #509)
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13
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Peng XL, Zhao WJ, Wang YS, Dai KL, Cen YK, Liu ZQ, Zheng YG. Enhancement of gibberellic acid production from Fusarium fujikuroi by mutation breeding and glycerol addition. 3 Biotech 2020; 10:312. [PMID: 32582509 DOI: 10.1007/s13205-020-02303-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 06/12/2020] [Indexed: 10/24/2022] Open
Abstract
Gibberellic acid (GA3) is a natural plant growth hormone that has been widely used in agriculture and horticulture. To obtain higher GA3 producing strains, the method of screening the strains for resistance to simvastatin was used after treatment with nitrosoguanidine (NTG) and gamma rays. The rationale for the strategy was that mutants showing simvastatin resistance were likely to be high GA3 producers, as their activity of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase is relatively more effective. GA3 yield of mutant S109 increased by 14.2% than that of the original strain. The GA3 production ability in mutant S109 remained relatively stable after ten generations. With the addition of 0.4 g glycerol on the 5th day during the fermentation process in Erlenmeyer flask, maximum GA3 production of 2.7 g/L was achieved by this mutant, exhibiting 28.6% increase compared with original strain. Furthermore, we also achieved 2.8 g/L GA3 and had a 33.3% increase with addition 20 g glycerol on the 5th day during the fermentation process in a 5-L bioreactor. Our results indicated efficient GA3 production could be achieved on the condition that the supply of glycerol at the suitable conditions. This study would lay a foundation for industrial production of GA3.
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14
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Yue SJ, Huang P, Li S, Jan M, Hu HB, Wang W, Zhang XH. Enhanced Production of 2-Hydroxyphenazine from Glycerol by a Two-Stage Fermentation Strategy in Pseudomonas chlororaphis GP72AN. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2020; 68:561-566. [PMID: 31840510 DOI: 10.1021/acs.jafc.9b05033] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
2-Hydroxyphenazine (2-OH-PHZ) is an effective biocontrol antibiotic secreted by Pseudomonas chlororaphis GP72AN and is transformed from phenazine-1-carboxylic acid (PCA). PCA is the main component of the recently registered biopesticide "Shenqinmycin". Previous research showed that 2-OH-PHZ was better in controlling wheat take-all disease than PCA; however, 2-OH-PHZ production was low under natural conditions. Herein, we confirmed that PCA induced reactive oxygen species in its host P. chlororaphis GP72AN and that the addition of DTT improved PCA production by 1.8-fold, whereas the supplementation of K3[Fe(CN)6] and H2O2 increased the conversion rate of PCA to 2-OH-PHZ. Finally, a two-stage fermentation strategy combining the addition of DTT at 12 h and H2O2 at 24 h enhanced 2-OH-PHZ production. Taken together, the two-stage fermentation strategy was designed to enhance 2-OH-PHZ production for the first time, and it provided a valuable reference for the fermentation of other antibiotics.
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15
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Chen X, Ma D, Liu J, Luo Q, Liu L. Engineering the transmission efficiency of the noncyclic glyoxylate pathway for fumarate production in Escherichia coli. BIOTECHNOLOGY FOR BIOFUELS 2020; 13:132. [PMID: 32760446 PMCID: PMC7379832 DOI: 10.1186/s13068-020-01771-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Accepted: 07/15/2020] [Indexed: 05/16/2023]
Abstract
BACKGROUND Fumarate is a multifunctional dicarboxylic acid in the tricarboxylic acid cycle, but microbial engineering for fumarate production is limited by the transmission efficiency of its biosynthetic pathway. RESULTS Here, pathway engineering was used to construct the noncyclic glyoxylate pathway for fumarate production. To improve the transmission efficiency of intermediate metabolites, pathway optimization was conducted by fluctuating gene expression levels to identify potential bottlenecks and then remove them, resulting in a large increase in fumarate production from 8.7 to 16.2 g/L. To further enhance its transmission efficiency of targeted metabolites, transporter engineering was used by screening the C4-dicarboxylate transporters and then strengthening the capacity of fumarate export, leading to fumarate production up to 18.9 g/L. Finally, the engineered strain E. coli W3110△4-P(H)CAI(H)SC produced 22.4 g/L fumarate in a 5-L fed-batch bioreactor. CONCLUSIONS In this study, we offered rational metabolic engineering and flux optimization strategies for efficient production of fumarate. These strategies have great potential in developing efficient microbial cell factories for production of high-value added chemicals.
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Affiliation(s)
- Xiulai Chen
- State Key Laboratory of Food Science and Technology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122 China
- Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, Wuxi, 214122 China
- International Joint Laboratory on Food Safety, Jiangnan University, Wuxi, 214122 China
| | - Danlei Ma
- State Key Laboratory of Food Science and Technology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122 China
- Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, Wuxi, 214122 China
- International Joint Laboratory on Food Safety, Jiangnan University, Wuxi, 214122 China
| | - Jia Liu
- State Key Laboratory of Food Science and Technology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122 China
- Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, Wuxi, 214122 China
- International Joint Laboratory on Food Safety, Jiangnan University, Wuxi, 214122 China
| | - Qiuling Luo
- State Key Laboratory of Food Science and Technology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122 China
- Wuxi Chenming Biotechnology Co. Ltd, Wuxi, 214100 China
| | - Liming Liu
- State Key Laboratory of Food Science and Technology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122 China
- Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, Wuxi, 214122 China
- International Joint Laboratory on Food Safety, Jiangnan University, Wuxi, 214122 China
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16
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Westbrook AW, Miscevic D, Kilpatrick S, Bruder MR, Moo-Young M, Chou CP. Strain engineering for microbial production of value-added chemicals and fuels from glycerol. Biotechnol Adv 2019; 37:538-568. [DOI: 10.1016/j.biotechadv.2018.10.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2017] [Revised: 10/03/2018] [Accepted: 10/10/2018] [Indexed: 12/22/2022]
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17
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Microbial Production of Fatty Acid via Metabolic Engineering and Synthetic Biology. BIOTECHNOL BIOPROC E 2019. [DOI: 10.1007/s12257-018-0374-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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18
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Zhang X, Zhang D, Zhu J, Liu W, Xu G, Zhang X, Shi J, Xu Z. High-yield production of L-serine from glycerol by engineered Escherichia coli. J Ind Microbiol Biotechnol 2019; 46:221-230. [PMID: 30600411 DOI: 10.1007/s10295-018-2113-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Accepted: 11/20/2018] [Indexed: 01/19/2023]
Abstract
L-Serine is widely used in pharmaceutical, food and cosmetic industries, and the direct fermentation to produce L-serine from cheap carbon sources such as glycerol is greatly desired. The production of L-serine by engineered Escherichia coli from glycerol has not been achieved so far. In this study, E. coli was engineered to efficiently produce L-serine from glycerol. To this end, three L-serine deaminase genes were deleted in turn, and all of the deletions caused the maximal accumulation of L-serine at 0.06 g/L. Furthermore, removal of feedback inhibition by L-serine resulted in a titer of 1.1 g/L. Additionally, adaptive laboratory evolution was employed to improve glycerol utilization in combination with the overexpression of the cysteine/acetyl serine transporter gene eamA, leading to 2.36 g/L L-serine (23.6% of the theoretical yield). In 5-L bioreactor, L-serine titer could reach up to 7.53 g/L from glycerol, demonstrating the potential of the established strain and bioprocess.
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Affiliation(s)
- Xiaomei Zhang
- Laboratory of Pharmaceutical Engineering, School of Pharmaceutics Science, Jiangnan University, Wuxi, People's Republic of China
| | - Dong Zhang
- Laboratory of Pharmaceutical Engineering, School of Pharmaceutics Science, Jiangnan University, Wuxi, People's Republic of China
| | - Jiafen Zhu
- Laboratory of Pharmaceutical Engineering, School of Pharmaceutics Science, Jiangnan University, Wuxi, People's Republic of China
| | - Wang Liu
- Laboratory of Pharmaceutical Engineering, School of Pharmaceutics Science, Jiangnan University, Wuxi, People's Republic of China
| | - Guoqiang Xu
- National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, Wuxi, 214122, People's Republic of China.,The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, People's Republic of China
| | - Xiaojuan Zhang
- National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, Wuxi, 214122, People's Republic of China.,The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, People's Republic of China
| | - Jinsong Shi
- Laboratory of Pharmaceutical Engineering, School of Pharmaceutics Science, Jiangnan University, Wuxi, People's Republic of China
| | - Zhenghong Xu
- National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, Wuxi, 214122, People's Republic of China. .,The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, People's Republic of China.
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Cheng KK, Zeng J, Jian JH, Zhu JF, Zhang GX, Liu DH. Model-based temperature control for improving lactic acid production from glycerol. RSC Adv 2019; 9:11614-11620. [PMID: 35517023 PMCID: PMC9063304 DOI: 10.1039/c9ra01323g] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Accepted: 04/01/2019] [Indexed: 11/25/2022] Open
Abstract
To maximize the final lactic acid productivity and concentration, temperature control was optimized using a mathematical modelling approach. A kinetic model, including cell growth, product formation and substrate consumption equations, was proposed to describe the lactic acid production process by Escherichia coli AC-521 with glycerol as the substrate. By constructing four functions, the temperature effect was introduced on the fermentation process, where four parameters (Xmax, μmax, Yps and β) were observed to be significantly affected by the temperature. For the convenience of application, the temperature control strategies were simplified by dividing the whole fermentation process into several units. In each unit, the temperature was controlled constantly. Based on the model, the optimal temperature for each unit was determined to maximize the final lactate productivity. This temperature control strategy can be effectively applied in batch and fed-batch cultures, and the verified experimental evaluation showed a good correlation with the model data. Under improved temperature control conditions, a maximal lactic acid concentration of 90.4 g L−1 was obtained after 80 h of fed-batch fermentation, giving a productivity of 1.13 g L−1 h−1, which is 1.2 times more than that in the conventional constant temperature during the cultivation course. With model-based temperature control, yield of lactic acid obtained was higher than that obtained in the conventional process with a constant temperature.![]()
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Affiliation(s)
- Ke-Ke Cheng
- China-Latin America Joint Laboratory for Clean Energy and Climate Change
- School of Chemical Engineering and Energy Technology
- Dongguan University of Technology
- Dongguan
- China
| | - Jing Zeng
- Tsinghua Innovation Center in Dongguan
- Dongguan 523808
- China
| | - Jing-Hai Jian
- Tsinghua Innovation Center in Dongguan
- Dongguan 523808
- China
| | - Jun-Fan Zhu
- China-Latin America Joint Laboratory for Clean Energy and Climate Change
- School of Chemical Engineering and Energy Technology
- Dongguan University of Technology
- Dongguan
- China
| | - Gui-Xing Zhang
- China-Latin America Joint Laboratory for Clean Energy and Climate Change
- School of Chemical Engineering and Energy Technology
- Dongguan University of Technology
- Dongguan
- China
| | - De-Hua Liu
- Department of Chemical Engineering
- Tsinghua University
- Beijing 100084
- China
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20
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Yang J, Zhu Y, Qu G, Zeng Y, Tian C, Dong C, Men Y, Dai L, Sun Z, Sun Y, Ma Y. Biosynthesis of dendroketose from different carbon sources using in vitro and in vivo metabolic engineering strategies. BIOTECHNOLOGY FOR BIOFUELS 2018; 11:290. [PMID: 30386427 PMCID: PMC6202814 DOI: 10.1186/s13068-018-1293-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Accepted: 10/15/2018] [Indexed: 06/08/2023]
Abstract
BACKGROUND Asymmetric aldol-type C-C bond formation with ketones used as electrophilic receptor remains a challenging reaction for aldolases as biocatalysts. To date, only one kind of dihydroxyacetone phosphate (DHAP)-dependent aldolases has been discovered and applied to synthesize branched-chain sugars directly using DHAP and dihydroxyacetone (DHA) as substrate. However, the unstable and high-cost properties of DHAP limit large-scale application. Therefore, biosynthesis of branched-chain sugar from low-cost and abundant carbon sources is essential. RESULTS The detailed catalytic property of l-rhamnulose-1-phosphate aldolase (RhaD) and l-fuculose-1-phosphate aldolase (FucA) from Escherichia coli in catalyzing the aldol reactions with DHA as electrophilic receptors was characterized. Furthermore, we calculated the Bürgi-Dunitz trajectory using molecular dynamics simulations, thereby revealing the original sources of the catalytic efficiency of RhaD and FucA. A multi-enzyme reaction system composed of formolase, DHA kinase, RhaD, fructose-1-phosphatase, and polyphosphate kinase was constructed to in vitro produce dendroketose, a branched-chain sugar, from one-carbon formaldehyde. The conversion rate reached 86% through employing a one-pot, two-stage reaction process. Moreover, we constructed two artificial pathways in Corynebacterium glutamicum to obtain this product in vivo starting from glucose or glycerol. Fermentation with glycerol as feedstock produced 6.4 g/L dendroketose with a yield of 0.45 mol/mol glycerol, representing 90% of the maximum theoretical value. Additionally, the dendroketose production reached 36.3 g/L with a yield of 0.46 mol/mol glucose when glucose served as the sole carbon resource. CONCLUSIONS The detailed enzyme kinetics data of the two DHAP-dependent aldolases with DHA as electrophilic receptors were presented in this study. In addition, insights into this catalytic property were given via in silico simulations. Moreover, the cost-effective synthesis of dendroketose starting from one-, three-, and six-carbon resources was achieved through in vivo and in vitro metabolic engineering strategies. This rare branched-chain ketohexose may serve as precursor to prepare 4-hydroxymethylfurfural and branched-chain alkanes using chemical method.
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Affiliation(s)
- Jiangang Yang
- National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308 China
| | - Yueming Zhu
- National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308 China
| | - Ge Qu
- National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308 China
| | - Yan Zeng
- National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308 China
| | - Chaoyu Tian
- National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308 China
| | - Caixia Dong
- School of Pharmacy, Tianjin Medical University, Tianjin, China
| | - Yan Men
- National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308 China
| | - Longhai Dai
- National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308 China
| | - Zhoutong Sun
- National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308 China
| | - Yuanxia Sun
- National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308 China
| | - Yanhe Ma
- National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308 China
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21
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Doi Y. Lactic acid fermentation is the main aerobic metabolic pathway in Enterococcus faecalis metabolizing a high concentration of glycerol. Appl Microbiol Biotechnol 2018; 102:10183-10192. [DOI: 10.1007/s00253-018-9351-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Revised: 08/18/2018] [Accepted: 08/27/2018] [Indexed: 10/28/2022]
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22
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Riaz S, Fatima N, Rasheed A, Riaz M, Anwar F, Khatoon Y. Metabolic Engineered Biocatalyst: A Solution for PLA Based Problems. Int J Biomater 2018; 2018:1963024. [PMID: 30302092 PMCID: PMC6158955 DOI: 10.1155/2018/1963024] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Accepted: 08/29/2018] [Indexed: 11/18/2022] Open
Abstract
Polylactic acid (PLA) is a biodegradable thermoplastic polyester. In 2010, PLA became the second highest consumed bioplastic in the world due to its wide application. Conventionally, PLA is produced by direct condensation of lactic acid monomer and ring opening polymerization of lactide, resulting in lower molecular weight and lesser strength of polymer. Furthermore, conventional methods of PLA production require a catalyst which makes it inappropriate for biomedical applications. Newer method utilizes metabolic engineering of microorganism for direct production of PLA through fermentation which produces good quality and high molecular weight and yield as compared to conventional methods. PLA is used as decomposing packaging material, sheet casting, medical implants in the form of screw, plate, and rod pin, etc. The main focus of the review is to highlight the synthesis of PLA by various polymerization methods that mainly include metabolic engineering fermentation as well as salient biomedical applications of PLA.
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Affiliation(s)
- Sundus Riaz
- Department of Biomedical Engineering and Sciences, National University of Sciences & Technology, Islamabad, Pakistan
- Pakistan Agricultural Research Council, FQSRI, SARC, Karachi, Pakistan
| | - Nosheen Fatima
- Department of Biomedical Engineering and Sciences, National University of Sciences & Technology, Islamabad, Pakistan
| | - Ahmed Rasheed
- PhD. Scholar, Sun Yat-Sen University (East Campus), Higher Education Mega Centre North, Guangzhou, China
| | | | - Faiza Anwar
- Pakistan Agricultural Research Council, FQSRI, SARC, Karachi, Pakistan
| | - Yamna Khatoon
- Postgraduate Scholar, Department of Agriculture and Agribusiness Management, University of Karachi, Karachi, Pakistan
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23
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Zavrazhnov SA, Esipovich AL, Danov SM, Zlobin SY, Belousov AS. Catalytic Conversion of Glycerol to Lactic Acid: State of the Art and Prospects. KINETICS AND CATALYSIS 2018. [DOI: 10.1134/s0023158418040171] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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24
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Construction of an alternative glycerol-utilization pathway for improved β-carotene production in Escherichia coli. ACTA ACUST UNITED AC 2018; 45:697-705. [DOI: 10.1007/s10295-018-2045-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 05/04/2018] [Indexed: 01/27/2023]
Abstract
Abstract
Glycerol, which is an inevitable by-product of biodiesel production, is an ideal carbon source for the production of carotenoids due to its low price, good availability and chemically reduced status, which results in a low requirement for additional reducing equivalents. In this study, an alternative carbon-utilization pathway was constructed in Escherichia coli to enable more efficient β-carotene production from glycerol. An aldehyde reductase gene (alrd) and an aldehyde dehydrogenase gene (aldH) from Ralstonia eutropha H16 were integrated into the E. coli chromosome to form a novel glycerol-utilization pathway. The β-carotene specific production value was increased by 50% after the introduction of alrd and aldH. It was found that the glycerol kinase gene (garK), alrd and aldH were the bottleneck of the alternative glycerol metabolic pathway, and modulation of garK gene with an mRS library further increased the β-carotene specific production value by 13%. Finally, co-modulation of genes in the introduced aldH–alrd operon led to 86% more of β-carotene specific production value than that of the strain without the alternative glycerol-utilization pathway and the glycerol-utilization rate was also increased. In this work, β-carotene production of E. coli was significantly improved by constructing and optimizing an alternative glycerol-utilization pathway. This strategy can potentially be used to improve the production of other isoprenoids using glycerol as a cheap and abundant substrate, and therefore has industrial relevance.
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25
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Novak K, Flöckner L, Erian AM, Freitag P, Herwig C, Pflügl S. Characterizing the effect of expression of an acetyl-CoA synthetase insensitive to acetylation on co-utilization of glucose and acetate in batch and continuous cultures of E. coli W. Microb Cell Fact 2018; 17:109. [PMID: 29986728 PMCID: PMC6036698 DOI: 10.1186/s12934-018-0955-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Accepted: 07/02/2018] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND Due to its high stress tolerance and low acetate secretion, Escherichia coli W is reported to be a good production host for several metabolites and recombinant proteins. However, simultaneous co-utilization of glucose and other substrates such as acetate remains a challenge. The activity of acetyl-CoA-synthetase, one of the key enzymes involved in acetate assimilation is tightly regulated on a transcriptional and post-translational level. The aim of this study was to engineer E. coli W for overexpression of an acetylation insensitive acetyl-CoA-synthetase and to characterize this strain in batch and continuous cultures using glucose, acetate and during co-utilization of both substrates. RESULTS Escherichia coli W engineered to overexpress an acetylation-insensitive acetyl-CoA synthetase showed a 2.7-fold increase in acetate uptake in a batch process containing glucose and high concentrations of acetate compared to a control strain, indicating more efficient co-consumption of glucose and acetate. When acetate was used as the carbon source, batch duration could significantly be decreased in the overexpression strain, possibly due to alleviation of acetate toxicity. Chemostat cultivations with different dilution rates using glucose revealed only minor differences between the overexpression and control strain. Accelerostat cultivations using dilution rates between 0.20 and 0.70 h-1 indicated that E. coli W is naturally capable of efficiently co-utilizing glucose and acetate over a broad range of specific growth rates. Expression of acetyl-CoA synthetase resulted in acetate and glucose accumulation at lower dilution rates compared to the control strain. This observation can possibly be attributed to a higher ratio between acs and pta-ackA in the overexpression strain as revealed by gene expression analysis. This would result in enhanced energy dissipation caused by an imbalance in the Pta-AckA-Acs cycle. Furthermore, yjcH and actP, genes co-transcribed with acetyl-CoA synthetase showed significant down-regulation at elevated dilution rates. CONCLUSIONS Escherichia coli W expressing an acetylation-insensitive acetyl-CoA synthetase was shown to be a promising candidate for mixed feed processes using glucose and acetate. Comparison between batch and continuous cultures revealed distinct differences in glucose-acetate co-utilization behavior, requiring additional investigations such as multi-omics analysis and further engineering towards even more efficient co-utilization strains of E. coli W.
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Affiliation(s)
- Katharina Novak
- Research Area Biochemical Engineering, Institute for Chemical, Environmental and Bioscience Engineering, Technische Universität Wien, Gumpendorfer Straße 1a, 1060 Vienna, Austria
| | - Lukas Flöckner
- Research Area Biochemical Engineering, Institute for Chemical, Environmental and Bioscience Engineering, Technische Universität Wien, Gumpendorfer Straße 1a, 1060 Vienna, Austria
| | - Anna Maria Erian
- Research Area Biochemical Engineering, Institute for Chemical, Environmental and Bioscience Engineering, Technische Universität Wien, Gumpendorfer Straße 1a, 1060 Vienna, Austria
| | - Philipp Freitag
- Research Area Biochemical Engineering, Institute for Chemical, Environmental and Bioscience Engineering, Technische Universität Wien, Gumpendorfer Straße 1a, 1060 Vienna, Austria
| | - Christoph Herwig
- Research Area Biochemical Engineering, Institute for Chemical, Environmental and Bioscience Engineering, Technische Universität Wien, Gumpendorfer Straße 1a, 1060 Vienna, Austria
- Christian Doppler Laboratory for Mechanistic and Physiological Methods for Improved Bioprocesses, Gumpendorfer Straße 1a, 1060 Vienna, Austria
| | - Stefan Pflügl
- Research Area Biochemical Engineering, Institute for Chemical, Environmental and Bioscience Engineering, Technische Universität Wien, Gumpendorfer Straße 1a, 1060 Vienna, Austria
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Garg S, Clomburg JM, Gonzalez R. A modular approach for high-flux lactic acid production from methane in an industrial medium using engineered Methylomicrobium buryatense 5GB1. J Ind Microbiol Biotechnol 2018; 45:379-391. [PMID: 29675615 DOI: 10.1007/s10295-018-2035-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Accepted: 04/03/2018] [Indexed: 12/01/2022]
Abstract
Convergence of market drivers such as abundant availability of inexpensive natural gas and increasing awareness of its global warming effects have created new opportunities for the development of small-scale gas-to-liquid (GTL) conversion technologies that can efficiently utilize methane, the primary component of natural gas. Leveraging the unique ability of methanotrophs that use methane as carbon and energy source, biological GTL platforms can be envisioned that are readily deployable at remote petroleum drilling sites where large chemical GTL infrastructure is uneconomical to set-up. Methylomicrobium buryatense, an obligate methanotroph, has gained traction as a potential industrial methanotrophic host because of availability of genetic tools and recent advances in its metabolic engineering. However, progress is impeded by low strain performance and lack of an industrial medium. In this study, we first established a small-scale cultivation platform using Hungate tubes for growth of M. buryatense at medium-to-high-throughput that also enabled 2X faster growth compared to that obtained in traditional glass serum bottles. Then, employing a synthetic biology approach we engineered M. buryatense with varying promoter (inducible and constitutive) and ribosome-binding site combinations, and obtained a strain capable of producing L-lactate from methane at a flux 14-fold higher than previously reported. Finally, we demonstrated L-lactate production in an industrial medium by replacing nitrate with less-expensive ammonium as the nitrogen source. Under these conditions, L-lactate was synthesized at a flux approximately 50-fold higher than that reported previously in a bioreactor system while achieving a titer of 0.6 g/L. These findings position M. buryatense closer to becoming an industrial host strain of choice, and pave new avenues for accelerating methane-to-chemical conversion using synthetic biology.
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Affiliation(s)
- Shivani Garg
- Department of Chemical and Biomolecular Engineering, Rice University, 6100 Main Street MS-667, Houston, TX, 77005, USA
| | - James M Clomburg
- Department of Chemical and Biomolecular Engineering, Rice University, 6100 Main Street MS-667, Houston, TX, 77005, USA
| | - Ramon Gonzalez
- Department of Chemical and Biomolecular Engineering, Rice University, 6100 Main Street MS-667, Houston, TX, 77005, USA. .,Department of Bioengineering, Rice University, Houston, 77005, USA.
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Kumar V, Park S. Potential and limitations of Klebsiella pneumoniae as a microbial cell factory utilizing glycerol as the carbon source. Biotechnol Adv 2018; 36:150-167. [DOI: 10.1016/j.biotechadv.2017.10.004] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 10/15/2017] [Accepted: 10/16/2017] [Indexed: 12/16/2022]
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28
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Pradima J, Kulkarni MR, Archna. Review on enzymatic synthesis of value added products of glycerol, a by-product derived from biodiesel production. RESOURCE-EFFICIENT TECHNOLOGIES 2017. [DOI: 10.1016/j.reffit.2017.02.009] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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29
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Clomburg JM, Contreras SC, Chou A, Siegel JB, Gonzalez R. Combination of type II fatty acid biosynthesis enzymes and thiolases supports a functional β-oxidation reversal. Metab Eng 2017; 45:11-19. [PMID: 29146470 DOI: 10.1016/j.ymben.2017.11.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Revised: 10/13/2017] [Accepted: 11/04/2017] [Indexed: 01/05/2023]
Abstract
An engineered reversal of the β-oxidation cycle (r-BOX) and the fatty acid biosynthesis (FAB) pathway are promising biological platforms for advanced fuel and chemical production in part due to their iterative nature supporting the synthesis of various chain length products. While diverging in their carbon-carbon elongation reaction mechanism, iterative operation of each pathway relies on common chemical conversions (reduction, dehydration, and reduction) differing only in the attached moiety (acyl carrier protein (ACP) in FAB vs Coenzyme A in r-BOX). Given this similarity, we sought to determine whether FAB enzymes can be used in the context of r-BOX as a means of expanding available r-BOX components with a ubiquitous set of well characterized enzymes. Using enzymes from the type II FAB pathway (FabG, FabZ, and FabI) in conjunction with a thiolase catalyzing a non-decarboxylative condensation, we demonstrate that FAB enzymes support a functional r-BOX. Pathway operation with FAB enzymes was improved through computationally directed protein design to develop FabZ variants with amino acid substitutions designed to disrupt hydrogen bonding at the FabZ-ACP interface and introduce steric and electrostatic repulsion between the FabZ and ACP. FabZ with R126W and R121E substitutions resulted in improved carboxylic acid and alcohol production from one- and multiple-turn r-BOX compared to the wild-type enzyme. Furthermore, the ability for FAB enzymes to operate on functionalized intermediates was exploited to produce branched chain carboxylic acids through an r-BOX with functionalized priming. These results not only provide an expanded set of enzymes within the modular r-BOX pathway, but can also potentially expand the scope of products targeted through this pathway by operating with CoA intermediates containing various functional groups.
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Affiliation(s)
- James M Clomburg
- Department of Chemical and Biomolecular Engineering, Rice University, 6100 Main St, Houston, TX 77005, USA
| | - Stephanie C Contreras
- Department of Chemistry, University of California Davis, One Shields Avenue, Davis, CA 95616, USA; Genome Center, University of California Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Alexander Chou
- Department of Chemical and Biomolecular Engineering, Rice University, 6100 Main St, Houston, TX 77005, USA
| | - Justin B Siegel
- Department of Chemistry, University of California Davis, One Shields Avenue, Davis, CA 95616, USA; Biochemistry & Molecular Medicine, University of California Davis, One Shields Avenue, Davis, CA 95616, USA; Genome Center, University of California Davis, One Shields Avenue, Davis, CA 95616, USA.
| | - Ramon Gonzalez
- Department of Chemical and Biomolecular Engineering, Rice University, 6100 Main St, Houston, TX 77005, USA; Department of Bioengineering, Rice University, 6100 Main St, Houston, TX 77005, USA.
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30
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Abstract
Systems metabolic engineering, which recently emerged as metabolic engineering integrated with systems biology, synthetic biology, and evolutionary engineering, allows engineering of microorganisms on a systemic level for the production of valuable chemicals far beyond its native capabilities. Here, we review the strategies for systems metabolic engineering and particularly its applications in Escherichia coli. First, we cover the various tools developed for genetic manipulation in E. coli to increase the production titers of desired chemicals. Next, we detail the strategies for systems metabolic engineering in E. coli, covering the engineering of the native metabolism, the expansion of metabolism with synthetic pathways, and the process engineering aspects undertaken to achieve higher production titers of desired chemicals. Finally, we examine a couple of notable products as case studies produced in E. coli strains developed by systems metabolic engineering. The large portfolio of chemical products successfully produced by engineered E. coli listed here demonstrates the sheer capacity of what can be envisioned and achieved with respect to microbial production of chemicals. Systems metabolic engineering is no longer in its infancy; it is now widely employed and is also positioned to further embrace next-generation interdisciplinary principles and innovation for its upgrade. Systems metabolic engineering will play increasingly important roles in developing industrial strains including E. coli that are capable of efficiently producing natural and nonnatural chemicals and materials from renewable nonfood biomass.
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Lehning CE, Siedler S, Ellabaan MMH, Sommer MOA. Assessing glycolytic flux alterations resulting from genetic perturbations in E. coli using a biosensor. Metab Eng 2017; 42:194-202. [PMID: 28709932 PMCID: PMC5555440 DOI: 10.1016/j.ymben.2017.07.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Accepted: 07/11/2017] [Indexed: 11/19/2022]
Abstract
We describe the development of an optimized glycolytic flux biosensor and its application in detecting altered flux in a production strain and in a mutant library. The glycolytic flux biosensor is based on the Cra-regulated ppsA promoter of E. coli controlling fluorescent protein synthesis. We validated the glycolytic flux dependency of the biosensor in a range of different carbon sources in six different E. coli strains and during mevalonate production. Furthermore, we studied the flux-altering effects of genome-wide single gene knock-outs in E. coli in a multiplex FlowSeq experiment. From a library consisting of 2126 knock-out mutants, we identified 3 mutants with high-flux and 95 mutants with low-flux phenotypes that did not have severe growth defects. This approach can improve our understanding of glycolytic flux regulation improving metabolic models and engineering efforts.
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Affiliation(s)
- Christina E Lehning
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kemitorvet Building 220, 2800 Lyngby, Denmark
| | - Solvej Siedler
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kemitorvet Building 220, 2800 Lyngby, Denmark
| | - Mostafa M H Ellabaan
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kemitorvet Building 220, 2800 Lyngby, Denmark
| | - Morten O A Sommer
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kemitorvet Building 220, 2800 Lyngby, Denmark.
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Coordination of metabolic pathways: Enhanced carbon conservation in 1,3-propanediol production by coupling with optically pure lactate biosynthesis. Metab Eng 2017; 41:102-114. [PMID: 28396036 DOI: 10.1016/j.ymben.2017.03.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Revised: 01/09/2017] [Accepted: 03/31/2017] [Indexed: 11/23/2022]
Abstract
Metabolic engineering has emerged as a powerful tool for bioproduction of both fine and bulk chemicals. The natural coordination among different metabolic pathways contributes to the complexity of metabolic modification, which hampers the development of biorefineries. Herein, the coordination between the oxidative and reductive branches of glycerol metabolism was rearranged in Klebsiella oxytoca to improve the 1,3-propanediol production. After deliberating on the product value, carbon conservation, redox balance, biological compatibility and downstream processing, the lactate-producing pathway was chosen for coupling with the 1,3-propanediol-producing pathway. Then, the other pathways of 2,3-butanediol, ethanol, acetate, and succinate were blocked in sequence, leading to improved d-lactate biosynthesis, which as return drove the 1,3-propanediol production. Meanwhile, efficient co-production of 1,3-propanediol and l-lactate was also achieved by replacing ldhD with ldhL from Bacillus coagulans. The engineered strains PDL-5 and PLL co-produced over 70g/L 1,3-propanediol and over 100g/L optically pure d-lactate and l-lactate, respectively, with high conversion yields of over 0.95mol/mol from glycerol.
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Yang J, Zhu Y, Men Y, Sun S, Zeng Y, Zhang Y, Sun Y, Ma Y. Pathway Construction in Corynebacterium glutamicum and Strain Engineering To Produce Rare Sugars from Glycerol. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2016; 64:9497-9505. [PMID: 27998065 DOI: 10.1021/acs.jafc.6b03423] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Rare sugars are valuable natural products widely used in pharmaceutical and food industries. In this study, we expected to synthesize rare ketoses from abundant glycerol using dihydroxyacetone phosphate (DHAP)-dependent aldolases. First, a new glycerol assimilation pathway was constructed to synthesize DHAP. The enzymes which convert glycerol to 3-hydroxypropionaldehyde and l-glyceraldehyde were selected, and their corresponding aldehyde synthesis pathways were constructed in vivo. Four aldol pathways based on different aldolases and phosphorylase were gathered. Next, three pathways were assembled and the resulting strains synthesized 5-deoxypsicose, 5-deoxysorbose, and 5-deoxyfructose from glucose and glycerol and produce l-fructose, l-tagatose, l-sorbose, and l-psicose with glycerol as the only carbon source. To achieve higher product titer and yield, the recombinant strains were further engineered and fermentation conditions were optimized. Fed-batch culture of engineered strains obtained 38.1 g/L 5-deoxypsicose with a yield of 0.91 ± 0.04 mol product per mol of glycerol and synthesized 20.8 g/L l-fructose, 10.3 g/L l-tagatose, 1.2 g/L l-sorbose, and 0.95 g/L l-psicose.
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Affiliation(s)
- Jiangang Yang
- National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences , Tianjin 300308, China
| | - Yueming Zhu
- National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences , Tianjin 300308, China
| | - Yan Men
- National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences , Tianjin 300308, China
| | - Shangshang Sun
- National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences , Tianjin 300308, China
| | - Yan Zeng
- National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences , Tianjin 300308, China
| | - Ying Zhang
- National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences , Tianjin 300308, China
| | - Yuanxia Sun
- National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences , Tianjin 300308, China
| | - Yanhe Ma
- National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences , Tianjin 300308, China
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Wegener M, Vogtmann K, Huber M, Laass S, Soppa J. The glpD gene is a novel reporter gene for E. coli that is superior to established reporter genes like lacZ and gusA. J Microbiol Methods 2016; 131:181-187. [PMID: 27794441 DOI: 10.1016/j.mimet.2016.10.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Revised: 10/18/2016] [Accepted: 10/21/2016] [Indexed: 01/05/2023]
Abstract
Reporter genes facilitate the characterization of promoter activities, transcript stabilities, translational efficiencies, or intracellular localization. Various reporter genes for Escherichia coli have been established, however, most of them have drawbacks like transcript instability or the inability to be used in genetic selections. Therefore, the glpD gene encoding glycerol-3-phosphate dehydrogenase was introduced as a novel reporter gene for E. coli. The enzymatic assay was optimized, and it was verified that growth on glycerol strictly depends on the presence of GlpD. The 5'-UTRs of three E. coli genes were chosen and cloned upstream of the new reporter gene glpD as well as the established reporter genes lacZ and gusA. Protein and transcript levels were quantified and translational efficiencies were calculated. The lacZ transcript was very unstable and its level highly depended on its translation, compromising its use as a reporter. The results obtained with gusA and glpD were similar, however, only glpD can be used for genetic selections. Therefore, glpD was found to be a superior novel reporter gene compared to the established reporter genes lacZ and gusA.
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Affiliation(s)
- Marius Wegener
- Goethe-University, Biocentre, Institute for Molecular Biosciences, Max-von-Laue-Str. 9, D-60438 Frankfurt, Germany.
| | - Kristina Vogtmann
- Goethe-University, Biocentre, Institute for Molecular Biosciences, Max-von-Laue-Str. 9, D-60438 Frankfurt, Germany.
| | - Madeleine Huber
- Goethe-University, Biocentre, Institute for Molecular Biosciences, Max-von-Laue-Str. 9, D-60438 Frankfurt, Germany.
| | - Sebastian Laass
- Goethe-University, Biocentre, Institute for Molecular Biosciences, Max-von-Laue-Str. 9, D-60438 Frankfurt, Germany.
| | - Jörg Soppa
- Goethe-University, Biocentre, Institute for Molecular Biosciences, Max-von-Laue-Str. 9, D-60438 Frankfurt, Germany.
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Abdel-Rahman MA, Sonomoto K. Opportunities to overcome the current limitations and challenges for efficient microbial production of optically pure lactic acid. J Biotechnol 2016; 236:176-92. [DOI: 10.1016/j.jbiotec.2016.08.008] [Citation(s) in RCA: 114] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Accepted: 08/11/2016] [Indexed: 10/21/2022]
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de Lima PBA, Mulder KCL, Melo NTM, Carvalho LS, Menino GS, Mulinari E, de Castro VH, Dos Reis TF, Goldman GH, Magalhães BS, Parachin NS. Novel homologous lactate transporter improves L-lactic acid production from glycerol in recombinant strains of Pichia pastoris. Microb Cell Fact 2016; 15:158. [PMID: 27634467 PMCID: PMC5025603 DOI: 10.1186/s12934-016-0557-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2016] [Accepted: 09/08/2016] [Indexed: 01/17/2023] Open
Abstract
Background Crude glycerol is the main byproduct of the biodiesel industry. Although it can have different applications, its purification is costly. Therefore, in this study a biotechnological route has been proposed for further utilization of crude glycerol in the fermentative production of lactic acid. This acid is largely utilized in food, pharmaceutical, textile, and chemical industries, making it the hydroxycarboxylic acid with the highest market potential worldwide. Currently, industrial production of lactic acid is done mainly using sugar as the substrate. Thus here, for the first time, Pichia pastoris has been engineered for heterologous l-lactic acid production using glycerol as a single carbon source. For that, the Bos taurus lactate dehydrogenase gene was introduced into P. pastoris. Moreover, a heterologous and a novel homologous lactate transporter have been evaluated for l-lactic acid production. Results Batch fermentation of the P. pastoris X-33 strain producing LDHb allowed for lactic acid production in this yeast. Although P. pastoris is known for its respiratory metabolism, batch fermentations were performed with different oxygenation levels, indicating that lower oxygen availability increased lactic acid production by 20 %, pushing the yeast towards a fermentative metabolism. Furthermore, a newly putative lactate transporter from P. pastoris named PAS has been identified by search similarity with the lactate transporter from Saccharomyces cerevisiae Jen1p. Both heterologous and homologous transporters, Jen1p and PAS, were evaluated in one strain already containing LDH activity. Fed-batch experiments of P. pastoris strains carrying the lactate transporter were performed with the batch phase at aerobic conditions followed by an aerobic oxygen-limited phase where production of lactic acid was favored. The results showed that the strain containing PAS presented the highest lactic acid titer, reaching a yield of approximately 0.7 g/g. Conclusions We showed that P. pastoris has a great potential as a fermentative organism for producing l-lactic acid using glycerol as the carbon source at limited oxygenation conditions (below 0.05 % DO in the bioreactor). The best strain had both the LDHb and the homologous lactate transporter encoding genes expressed, and reached a titer 1.5 times higher than the strain with the S. cerevisiae transporter. Finally, it was also shown that increased lactic acid production was concomitant to reduction of acetic acid formation by half.
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Affiliation(s)
- Pollyne Borborema Almeida de Lima
- Grupo de Engenharia Metabólica Aplicada a Bioprocessos, Instituto de Ciências Biológicas, Universidade de Brasília, Brasília, DF, CEP 70.790-900, Brazil
| | - Kelly Cristina Leite Mulder
- Integra Bioprocessos e Análises, Campus Universitário Darcy Ribeiro, Edifício CDT, Sala AT-36/37, Brasília, DF, CEP 70.904-970, Brazil
| | - Nadiele Tamires Moreira Melo
- Pós-Graduação em Ciências Genômicas e Biotecnologia, Universidade Católica de Brasília, Brasília, DF, CEP 70.790-160, Brazil
| | - Lucas Silva Carvalho
- Pós-Graduação em Ciências Genômicas e Biotecnologia, Universidade Católica de Brasília, Brasília, DF, CEP 70.790-160, Brazil
| | - Gisele Soares Menino
- Integra Bioprocessos e Análises, Campus Universitário Darcy Ribeiro, Edifício CDT, Sala AT-36/37, Brasília, DF, CEP 70.904-970, Brazil
| | - Eduardo Mulinari
- Integra Bioprocessos e Análises, Campus Universitário Darcy Ribeiro, Edifício CDT, Sala AT-36/37, Brasília, DF, CEP 70.904-970, Brazil
| | - Virgilio H de Castro
- Integra Bioprocessos e Análises, Campus Universitário Darcy Ribeiro, Edifício CDT, Sala AT-36/37, Brasília, DF, CEP 70.904-970, Brazil
| | - Thaila F Dos Reis
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, São Paulo, CEP 14.040-903, Brazil
| | - Gustavo Henrique Goldman
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, São Paulo, CEP 14.040-903, Brazil
| | - Beatriz Simas Magalhães
- Pós-Graduação em Ciências Genômicas e Biotecnologia, Universidade Católica de Brasília, Brasília, DF, CEP 70.790-160, Brazil.,Integra Bioprocessos e Análises, Campus Universitário Darcy Ribeiro, Edifício CDT, Sala AT-36/37, Brasília, DF, CEP 70.904-970, Brazil
| | - Nádia Skorupa Parachin
- Grupo de Engenharia Metabólica Aplicada a Bioprocessos, Instituto de Ciências Biológicas, Universidade de Brasília, Brasília, DF, CEP 70.790-900, Brazil.
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Sun X, Shen X, Jain R, Lin Y, Wang J, Sun J, Wang J, Yan Y, Yuan Q. Synthesis of chemicals by metabolic engineering of microbes. Chem Soc Rev 2016; 44:3760-85. [PMID: 25940754 DOI: 10.1039/c5cs00159e] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Metabolic engineering is a powerful tool for the sustainable production of chemicals. Over the years, the exploration of microbial, animal and plant metabolism has generated a wealth of valuable genetic information. The prudent application of this knowledge on cellular metabolism and biochemistry has enabled the construction of novel metabolic pathways that do not exist in nature or enhance existing ones. The hand in hand development of computational technology, protein science and genetic manipulation tools has formed the basis of powerful emerging technologies that make the production of green chemicals and fuels a reality. Microbial production of chemicals is more feasible compared to plant and animal systems, due to simpler genetic make-up and amenable growth rates. Here, we summarize the recent progress in the synthesis of biofuels, value added chemicals, pharmaceuticals and nutraceuticals via metabolic engineering of microbes.
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Affiliation(s)
- Xinxiao Sun
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, 15#, Beisanhuan East Road, Chaoyang District, Beijing 100029, China.
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Escherichia coli enoyl-acyl carrier protein reductase (FabI) supports efficient operation of a functional reversal of β-oxidation cycle. Appl Environ Microbiol 2016; 81:1406-16. [PMID: 25527535 DOI: 10.1128/aem.03521-14] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
We recently used a synthetic/bottom-up approach to establish the identity of the four enzymes composing an engineered functional reversal of the -oxidation cycle for fuel and chemical production in Escherichia coli (J. M. Clomburg, J. E. Vick, M. D. Blankschien, M. Rodriguez-Moya, and R. Gonzalez, ACS Synth Biol 1:541–554, 2012, http://dx.doi.org/10.1021/sb3000782).While native enzymes that catalyze the first three steps of the pathway were identified, the identity of the native enzyme(s) acting as the trans-enoyl coenzyme A (CoA) reductase(s) remained unknown, limiting the amount of product that could be synthesized (e.g., 0.34 g/liter butyrate) and requiring the overexpression of a foreign enzyme (the Euglena gracilis trans-enoyl-CoA reductase [EgTER]) to achieve high titers (e.g., 3.4 g/liter butyrate). Here, we examine several native E. coli enzymes hypothesized to catalyze the reduction of enoyl-CoAs to acyl-CoAs. Our results indicate that FabI, the native enoyl-acyl carrier protein (enoyl-ACP) reductase (ENR) from type II fatty acid biosynthesis, possesses sufficient NADH-dependent TER activity to support the efficient operation of a -oxidation reversal. Overexpression of FabI proved as effective as EgTER for the production of butyrate and longer-chain carboxylic acids. Given the essential nature of fabI, we investigated whether bacterial ENRs from other families were able to complement a fabI deletion without promiscuous reduction of crotonyl-CoA. These characteristics from Bacillus subtilis FabL enabled deltaffabI complementation experiments that conclusively established that FabI encodes a native enoyl-CoA reductase activity that supports the β-oxidation reversal in E. coli.
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Chen Z, Liu D. Toward glycerol biorefinery: metabolic engineering for the production of biofuels and chemicals from glycerol. BIOTECHNOLOGY FOR BIOFUELS 2016; 9:205. [PMID: 27729943 PMCID: PMC5048440 DOI: 10.1186/s13068-016-0625-8] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 09/24/2016] [Indexed: 05/03/2023]
Abstract
As an inevitable by-product of the biofuel industry, glycerol is becoming an attractive feedstock for biorefinery due to its abundance, low price and high degree of reduction. Converting crude glycerol into value-added products is important to increase the economic viability of the biofuel industry. Metabolic engineering of industrial strains to improve its performance and to enlarge the product spectrum of glycerol biotransformation process is highly important toward glycerol biorefinery. This review focuses on recent metabolic engineering efforts as well as challenges involved in the utilization of glycerol as feedstock for the production of fuels and chemicals, especially for the production of diols, organic acids and biofuels.
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Affiliation(s)
- Zhen Chen
- Department of Chemical Engineering, Tsinghua University, Beijing, 100084 China
- Tsinghua Innovation Center in Dongguan, Dongguan, 523808 China
| | - Dehua Liu
- Department of Chemical Engineering, Tsinghua University, Beijing, 100084 China
- Tsinghua Innovation Center in Dongguan, Dongguan, 523808 China
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Hao G, Chen H, Gu Z, Zhang H, Chen W, Chen YQ. Metabolic engineering of Mortierella alpina for arachidonic acid production with glycerol as carbon source. Microb Cell Fact 2015; 14:205. [PMID: 26701302 PMCID: PMC4690419 DOI: 10.1186/s12934-015-0392-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 12/05/2015] [Indexed: 12/23/2022] Open
Abstract
Background Although some microorganisms can convert glycerol into valuable products such as polyunsaturated fatty acids, the yields are relative low due primarily to an inefficient assimilation of glycerol. Mortierella alpina is an oleaginous fungus which preferentially uses glucose over glycerol as the carbon source for fatty acid synthesis. Results In the present study, we metabolically engineered M. alpina to increase the utilization of glycerol. Glycerol kinase and glycerol-3-phosphate dehydrogenase control the first two steps of glycerol decomposition. GK overexpression increased the total fatty acid content by 35 %, whereas G3PD1, G3PD2 and G3PD3 had no significant effect. Overexpression of malic enzyme (ME1) but not glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase or isocitrate dehydrogenase significantly increased fatty acid content when glycerol was used as carbon source. Simultaneous overexpression of GK and ME1 enabled M. alpina to accumulate fatty acids efficiently, with a 44 % increase in fatty acid content (% of dry weight), a 57 % increase in glycerol to fatty acid yield (g/g glycerol) and an 81 % increase in fatty acid production (g/L culture). A repeated batch process was applied to relieve the inhibitory effect of raw glycerol on arachidonic acid synthesis, and under these conditions, the yield reached 52.2 ± 1.9 mg/g. Conclusions This study suggested that GK is a rate-limiting step in glycerol assimilation in M. alpina. Another restricting factor for fatty acid accumulation was the supply of cytosolic NADPH. We reported a bioengineering strategy by improving the upstream assimilation and NADPH supply, for oleaginous fungi to efficiently accumulate fatty acid with glycerol as carbon source. Electronic supplementary material The online version of this article (doi:10.1186/s12934-015-0392-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Guangfei Hao
- State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, Wuxi, 214122, People's Republic of China.
| | - Haiqin Chen
- State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, Wuxi, 214122, People's Republic of China. .,Synergistic Innovation Center for Food Safety and Nutrition, Wuxi, 214122, People's Republic of China.
| | - Zhennan Gu
- State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, Wuxi, 214122, People's Republic of China. .,Synergistic Innovation Center for Food Safety and Nutrition, Wuxi, 214122, People's Republic of China.
| | - Hao Zhang
- State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, Wuxi, 214122, People's Republic of China. .,Synergistic Innovation Center for Food Safety and Nutrition, Wuxi, 214122, People's Republic of China.
| | - Wei Chen
- State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, Wuxi, 214122, People's Republic of China. .,Synergistic Innovation Center for Food Safety and Nutrition, Wuxi, 214122, People's Republic of China. .,Beijing Innovation Centre of Food Nutrition and Human Health, Beijing Technology and Business University (BTBU), Beijing, 100048, People's Republic of China.
| | - Yong Q Chen
- State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, Wuxi, 214122, People's Republic of China. .,Synergistic Innovation Center for Food Safety and Nutrition, Wuxi, 214122, People's Republic of China. .,Departments of Cancer Biology and Biochemistry, Wake Forest School of Medicine, Winston-Salem, NC, 27157, USA.
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Wang ZW, Saini M, Lin LJ, Chiang CJ, Chao YP. Systematic Engineering of Escherichia coli for d-Lactate Production from Crude Glycerol. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2015; 63:9583-9. [PMID: 26477354 DOI: 10.1021/acs.jafc.5b04162] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Crude glycerol resulting from biodiesel production is an abundant and renewable resource. However, the impurities in crude glycerol usually make microbial fermentation problematic. This issue was addressed by systematic engineering of Escherichia coli for the production of d-lactate from crude glycerol. First, mgsA and the synthetic pathways of undesired products were eliminated in E. coli, rendering the strain capable of homofermentative production of optically pure d-lactate. To direct carbon flux toward d-lactate, the resulting strain was endowed with an enhanced expression of glpD-glpK in the glycerol catabolism and of a heterologous gene encoding d-lactate dehydrogenase. Moreover, the strain was evolved to improve its utilization of cruder glycerol and subsequently equipped with the FocA channel to export intracellular d-lactate. Finally, the fed-batch fermentation with two-phase culturing was carried out with a bioreactor. As a result, the engineered strain enabled production of 105 g/L d-lactate (99.9% optical purity) from 121 g/L crude glycerol at 40 h. The result indicates the feasibility of our approach to engineering E. coli for the crude glycerol-based fermentation.
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Affiliation(s)
- Zei Wen Wang
- Department of Chemical Engineering, Feng Chia University , 100 Wenhwa Road, Taichung 40724, Taiwan
| | - Mukesh Saini
- Department of Chemical Engineering, Feng Chia University , 100 Wenhwa Road, Taichung 40724, Taiwan
| | - Li-Jen Lin
- School of Chinese Medicine, College of Chinese Medicine, China Medical University , Taichung 40402, Taiwan
| | - Chung-Jen Chiang
- Department of Medical Laboratory Science and Biotechnology, China Medical University , No. 91, Hsueh-Shih Road, Taichung 40402, Taiwan
| | - Yun-Peng Chao
- Department of Chemical Engineering, Feng Chia University , 100 Wenhwa Road, Taichung 40724, Taiwan
- Department of Health and Nutrition Biotechnology, Asia University , Taichung 41354, Taiwan
- Department of Medical Research, China Medical University Hospital , Taichung 40447, Taiwan
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Recent advances in microbial production of fuels and chemicals using tools and strategies of systems metabolic engineering. Biotechnol Adv 2015; 33:1455-66. [DOI: 10.1016/j.biotechadv.2014.11.006] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Revised: 10/23/2014] [Accepted: 11/09/2014] [Indexed: 11/22/2022]
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Affiliation(s)
- Veeresh Juturu
- Institute of Chemical and Engineering Sciences, Agency for Science, Technology and Research (A*STAR), Jurong Island, Singapore
| | - Jin Chuan Wu
- Institute of Chemical and Engineering Sciences, Agency for Science, Technology and Research (A*STAR), Jurong Island, Singapore
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Metabolic engineering of Escherichia coli to enhance acetol production from glycerol. Appl Microbiol Biotechnol 2015; 99:7945-52. [PMID: 26078109 DOI: 10.1007/s00253-015-6732-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Revised: 05/17/2015] [Accepted: 05/27/2015] [Indexed: 12/22/2022]
Abstract
Acetol, a C3 keto alcohol, is an important intermediate used to produce polyols and acrolein. To enhance acetol production from glycerol by Escherichia coli, a mutant (HJ02) was constructed by replacing the native glpK gene with the allele from E. coli Lin 43 and overexpression of yqhD, which encodes aldehyde oxidoreductase YqhD that converts methylglyoxal to acetol. Compared to the control strain without the glpK replacement, HJ02 had 5.5 times greater acetol production and a 53.4 % higher glycerol consumption rate. Then, glucose was added as a co-substrate to enhance NADPH availability and the ptsG gene was deleted in HJ02 (HJ04) to alleviate carbon catabolite repression, which led to a 30 % increase in the NADPH level and NADPH/NADP(+). Consequently, HJ04 accumulated up to 1.20 g/L of acetol, which is 69.0 % higher than that of HJ02. Furthermore, the gapA gene in HJ04 was silenced by antisense RNA (HJ05) to further enhance acetol production. The acetol concentration produced by HJ05 reached 1.82 g/L, which was 2.1 and 1.5 times higher than that of HJ02 and HJ04.Real-time PCR analysis indicates that glucose catabolism was rerouted from glycolysis to the oxidative pentose phosphate pathway in HJ05.
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Integrated engineering of β-oxidation reversal and ω-oxidation pathways for the synthesis of medium chain ω-functionalized carboxylic acids. Metab Eng 2015; 28:202-212. [DOI: 10.1016/j.ymben.2015.01.007] [Citation(s) in RCA: 103] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Revised: 01/05/2015] [Accepted: 01/20/2015] [Indexed: 12/28/2022]
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Becker J, Wittmann C. Advanced Biotechnology: Metabolically Engineered Cells for the Bio-Based Production of Chemicals and Fuels, Materials, and Health-Care Products. Angew Chem Int Ed Engl 2015; 54:3328-50. [DOI: 10.1002/anie.201409033] [Citation(s) in RCA: 223] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Indexed: 12/16/2022]
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Biotechnologie von Morgen: metabolisch optimierte Zellen für die bio-basierte Produktion von Chemikalien und Treibstoffen, Materialien und Gesundheitsprodukten. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201409033] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Kim S, Clomburg JM, Gonzalez R. Synthesis of medium-chain length (C6-C10) fuels and chemicals via β-oxidation reversal in Escherichia coli. J Ind Microbiol Biotechnol 2015; 42:465-75. [PMID: 25645093 DOI: 10.1007/s10295-015-1589-6] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Accepted: 01/14/2015] [Indexed: 11/30/2022]
Abstract
The recently engineered reversal of the β-oxidation cycle has been proposed as a potential platform for the efficient synthesis of longer chain (C ≥ 4) fuels and chemicals. Here, we demonstrate the utility of this platform for the synthesis of medium-chain length (C6-C10) products through the manipulation of key components of the pathway. Deletion of endogenous thioesterases provided a clean background in which the expression of various thiolase and termination components, along with required core enzymes, resulted in the ability to alter the chain length distribution and functionality of target products. This approach enabled the synthesis of medium-chain length carboxylic acids and primary alcohols from glycerol, a low-value feedstock. The use of BktB as the thiolase component with thioesterase TesA' as the termination enzyme enabled the synthesis of about 1.3 g/L C6-C10 saturated carboxylic acids. Tailoring of product formation to primary alcohol synthesis was achieved with the use of various acyl-CoA reductases. The combination of AtoB and FadA as the thiolase components with the alcohol-forming acyl-CoA reductase Maqu2507 from M. aquaeolei resulted in the synthesis of nearly 0.3 g/L C6-C10 alcohols. These results further demonstrate the versatile nature of a β-oxidation reversal, and highlight several key aspects and control points that can be further manipulated to fine-tune the synthesis of various fuels and chemicals.
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Affiliation(s)
- Seohyoung Kim
- Department of Chemical and Biomolecular Engineering, Rice University, 6100 Main Street, MS-362, Houston, TX, 77005, USA
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Eiteman MA, Ramalingam S. Microbial production of lactic acid. Biotechnol Lett 2015; 37:955-72. [PMID: 25604523 DOI: 10.1007/s10529-015-1769-5] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Accepted: 01/07/2015] [Indexed: 10/24/2022]
Abstract
Lactic acid is an important commodity chemical having a wide range of applications. Microbial production effectively competes with chemical synthesis methods because biochemical synthesis permits the generation of either one of the two enantiomers with high optical purity at high yield and titer, a result which is particularly beneficial for the production of poly(lactic acid) polymers having specific properties. The commercial viability of microbial lactic acid production relies on utilization of inexpensive carbon substrates derived from agricultural or waste resources. Therefore, optimal lactic acid formation requires an understanding and engineering of both the competing pathways involved in carbohydrate metabolism, as well as pathways leading to potential by-products which both affect product yield. Recent research leverages those biochemical pathways, while researchers also continue to seek strains with improved tolerance and ability to perform under desirable industrial conditions, for example, of pH and temperature.
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Affiliation(s)
- Mark A Eiteman
- BioChemical Engineering Program, College of Engineering, University of Georgia, Athens, GA, 30602, USA,
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L-lactate production from biodiesel-derived crude glycerol by metabolically engineered Enterococcus faecalis: cytotoxic evaluation of biodiesel waste and development of a glycerol-inducible gene expression system. Appl Environ Microbiol 2015; 81:2082-9. [PMID: 25576618 DOI: 10.1128/aem.03418-14] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Biodiesel waste is a by-product of the biodiesel production process that contains a large amount of crude glycerol. To reuse the crude glycerol, a novel bioconversion process using Enterococcus faecalis was developed through physiological studies. The E. faecalis strain W11 could use biodiesel waste as a carbon source, although cell growth was significantly inhibited by the oil component in the biodiesel waste, which decreased the cellular NADH/NAD(+) ratio and then induced oxidative stress to cells. When W11 was cultured with glycerol, the maximum culture density (optical density at 600 nm [OD600]) under anaerobic conditions was decreased 8-fold by the oil component compared with that under aerobic conditions. Furthermore, W11 cultured with dihydroxyacetone (DHA) could show slight or no growth in the presence of the oil component with or without oxygen. These results indicated that the DHA kinase reaction in the glycerol metabolic pathway was sensitive to the oil component as an oxidant. The lactate dehydrogenase (Ldh) activity of W11 during anaerobic glycerol metabolism was 4.1-fold lower than that during aerobic glycerol metabolism, which was one of the causes of low l-lactate productivity. The E. faecalis pflB gene disruptant (Δpfl mutant) expressing the ldhL1LP gene produced 300 mM l-lactate from glycerol/crude glycerol with a yield of >99% within 48 h and reached a maximum productivity of 18 mM h(-1) (1.6 g liter(-1) h(-1)). Thus, our study demonstrates that metabolically engineered E. faecalis can convert crude glycerol to l-lactate at high conversion efficiency and provides critical information on the recycling process for biodiesel waste.
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