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Laksmi FA, Dewi KS, Nuryana I, Yulianti SE, Ramadhan KP, Hadi MI, Nugraha Y. High-level expression of codon-optimized Taq DNA polymerase under the control of rhaBAD promoter. Anal Biochem 2024; 692:115581. [PMID: 38815728 DOI: 10.1016/j.ab.2024.115581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Revised: 05/24/2024] [Accepted: 05/25/2024] [Indexed: 06/01/2024]
Abstract
A DNA polymerase from Thermus aquaticus remains the most popular among DNA polymerases. It was widely applied in various fields involving the application of polymerase chain reaction (PCR), implying the high commercial value of this enzyme. For this reason, an attempt to obtain a high yield of Taq DNA polymerase is continuously conducted. In this study, the l-rhamnose-inducible promoter rhaBAD was utilized due to its ability to produce recombinant protein under tight control in E. coli expression system. Instead of full-length Taq polymerase, an N-terminal deletion of Taq polymerase was selected. To obtain a high-level expression, we attempted to optimize the codon by reducing the rare codon and GC content, and in a second attempt, we optimized the culture conditions for protein expression. The production of Taq polymerase using the optimum culture condition improved the level of expression by up to 3-fold. This approach further proved that a high level of recombinant protein expression could be achieved by yielding a purified Taq polymerase of about 8.5 mg/L of culture. This is the first research publication on the production of Taq polymerase with N-terminal deletion in E. coli with the control of the rhaBAD promoter system.
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Affiliation(s)
- Fina Amreta Laksmi
- Research Center for Applied Microbiology, National Research and Innovation Agency, Jalan Raya Bogor KM 46, Cibinong, Bogor, 16911, West Java, Indonesia.
| | - Kartika Sari Dewi
- Research Center for Genetic Engineering, National Research and Innovation Agency, Jalan Raya Bogor KM 46, Cibinong, Bogor, 16911, West Java, Indonesia
| | - Isa Nuryana
- Research Center for Applied Microbiology, National Research and Innovation Agency, Jalan Raya Bogor KM 46, Cibinong, Bogor, 16911, West Java, Indonesia
| | - Siti Eka Yulianti
- Research Center for Applied Microbiology, National Research and Innovation Agency, Jalan Raya Bogor KM 46, Cibinong, Bogor, 16911, West Java, Indonesia
| | - Kharisma Panji Ramadhan
- Research Center for Applied Microbiology, National Research and Innovation Agency, Jalan Raya Bogor KM 46, Cibinong, Bogor, 16911, West Java, Indonesia
| | - Moch Irfan Hadi
- Department of Biology, Sunan Ampel State Islamic University, Surabaya, Indonesia
| | - Yudhi Nugraha
- Research Center for Molecular Biology Eijkman, National Research and Innovation Agency, Jalan Raya Bogor KM 46, Cibinong, Bogor, 16911, West Java, Indonesia.
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Wang H, Zhou W, Zhang Y, Wang C, Liu C, Xu J, Zhao Z, Liu H, Liu J, Ma Y. The synergistic effect of metal ions and amino acids on the fermentation of β-CGTase-producing statin DF257. 3 Biotech 2024; 14:53. [PMID: 38274847 PMCID: PMC10805693 DOI: 10.1007/s13205-023-03900-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Accepted: 12/18/2023] [Indexed: 01/27/2024] Open
Abstract
To meet the growing demand of β-cyclodextrin (CD), innovative approaches are being developed to improve the production of β-CD by β-cyclodextrin glucose-transferase (CGTase). Considering the low production and efficacy of wild-type β-CGTase-producing strains, to obtain the strains suitable for industrial production of β-CGTase, the recombinant engineered bacteria strain DF257 is constructed by transfecting with the plasmid expressing His tagged β-CGTase. The fermentation of β-CGTase-expressing DF257 was optimized in the presence of different metal ions, amino acids, and incubated at a certain temperature and pH condition. The results showed that when Mg2+ and isoleucine were added into the culture medium at 0.5 mM and 0.5 g/L, respectively, the enzyme activity of β-CGTase increased significantly after incubation at 37 °C with the initial pH of 7.5. In addition, the optimal temperature for β-CGTase with the addition of Mg2+ and isoleucine was also determined. The T half of β-CGTase under 50, 55, 60 and 65 °C was 9.5, 8.8, 6.2 and 1.2 h, respectively. Further investigation showed that β-CGTase kept stable under the pH 6.0-10.0, and pH 7.5 was identified as the optimal pH condition of β-CGTase. With the addition of Mg2+ and isoleucine, the kinetic properties of β-CGTase in the cyclization reaction had a similar form with Michaelis equation under 50 °C and pH 7.5, and Vmax, Km, and Kcat was 3.74 mg/mL/min, 3.28 mg/mL, and 31.17/s, respectively. The possible underlying mechanism by which Mg2+ and isoleucine synergistically improved the thermostability of β-CGTase was investigated by the surface hydrophobicity index analysis, Fourier transform infrared spectroscopy and differential scanning calorimetry (DSC) analysis. The results indicated that addition of Mg2+ and isoleucine maintained the spatial structure and enhanced the thermostability of β-CGTase. These findings provided a theoretical basis for realizing the industrialization application of β-CGTase in promoting the generation of β-CD.
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Affiliation(s)
- Hua Wang
- Inner Mongolia Minzu University, No. 996, Xilamulun Street, Horqin District, Tongliao City, 028043 Inner Mongolia China
| | - Wenxi Zhou
- Tongliao Academy of Agricultural and Animal Husbanddry Sciences, Tongliao City, 028043 Inner Mongolia China
| | - Yifan Zhang
- Inner Mongolia Minzu University, No. 996, Xilamulun Street, Horqin District, Tongliao City, 028043 Inner Mongolia China
| | - Cuifang Wang
- Inner Mongolia Minzu University, No. 996, Xilamulun Street, Horqin District, Tongliao City, 028043 Inner Mongolia China
| | - Chen Liu
- Inner Mongolia Minzu University, No. 996, Xilamulun Street, Horqin District, Tongliao City, 028043 Inner Mongolia China
| | - Jiahui Xu
- Inner Mongolia Minzu University, No. 996, Xilamulun Street, Horqin District, Tongliao City, 028043 Inner Mongolia China
| | - Zejun Zhao
- Inner Mongolia Minzu University, No. 996, Xilamulun Street, Horqin District, Tongliao City, 028043 Inner Mongolia China
| | - Hongyu Liu
- Inner Mongolia Minzu University, No. 996, Xilamulun Street, Horqin District, Tongliao City, 028043 Inner Mongolia China
| | - Jia Liu
- Inner Mongolia Minzu University, No. 996, Xilamulun Street, Horqin District, Tongliao City, 028043 Inner Mongolia China
| | - Yunxiao Ma
- Inner Mongolia Minzu University, No. 996, Xilamulun Street, Horqin District, Tongliao City, 028043 Inner Mongolia China
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Rabadiya K, Pardhi D, Thaker K, Patoliya J, Rajput K, Joshi R. A review on recent upgradation and strategies to enhance cyclodextrin glucanotransferase properties for its applications. Int J Biol Macromol 2024; 259:129315. [PMID: 38211906 DOI: 10.1016/j.ijbiomac.2024.129315] [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: 06/17/2023] [Revised: 12/27/2023] [Accepted: 01/05/2024] [Indexed: 01/13/2024]
Abstract
Cyclodextrin glycosyltransferase (CGTase) is a significant extracellular enzyme with diverse functions. CGTase is widely used in production of cyclic α-(1,4)-linked oligosaccharides (cyclodextrins) from starch via transglycosylation reaction. Recent discoveries of novel CGTases from different microorganisms have expanded its applications but natural CGTase have lower yield, leading to heterologous expression for increased production to meet various needs. Moreover, significant advancements in directed evolution approach have been explored to alter the molecular structure of CGTase to enhance its performance. This review comprehensively summarizes the strategies employed in heterologous expression to boost CGTase production and secretion in various host. It also outlines molecular engineering approaches aimed to improving CGTase properties, including product and substrate specificity, catalytic efficiency, and thermal stability. Additionally, a considerable stability against changes in temperature and organic solvents can be obtained by immobilization.
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Affiliation(s)
- Khushbu Rabadiya
- Department of Microbiology & Biotechnology, University School of Sciences, Gujarat University, Ahmedabad 380009, Gujarat, India.
| | - Dimple Pardhi
- Department of Microbiology & Biotechnology, University School of Sciences, Gujarat University, Ahmedabad 380009, Gujarat, India.
| | - Khushali Thaker
- Department of Biochemistry & Forensic Science, University School of Sciences, Gujarat University, Ahmedabad 380009, Gujarat, India.
| | - Jaimini Patoliya
- Department of Biochemistry & Forensic Science, University School of Sciences, Gujarat University, Ahmedabad 380009, Gujarat, India.
| | - Kiransinh Rajput
- Department of Microbiology & Biotechnology, University School of Sciences, Gujarat University, Ahmedabad 380009, Gujarat, India.
| | - Rushikesh Joshi
- Department of Biochemistry & Forensic Science, University School of Sciences, Gujarat University, Ahmedabad 380009, Gujarat, India.
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Pardhi DS, Rabadiya KJ, Panchal RR, Raval VH, Joshi RG, Rajput KN. Cyclodextrin glucanotransferase: fundamentals and biotechnological implications. Appl Microbiol Biotechnol 2023; 107:5899-5907. [PMID: 37548666 DOI: 10.1007/s00253-023-12708-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 07/21/2023] [Accepted: 07/25/2023] [Indexed: 08/08/2023]
Abstract
Cyclodextrin glucanotransferase (CGTase) is an extracellular enzyme of the GH13 α-amylase family that catalyzes a unique intramolecular reaction known as cyclization to transform α-1, 4-glucans and similar starches into cyclodextrins. They also catalyze intermolecular transglycosylation reactions namely coupling, disproportionation, and some hydrolyzing effects on starch. The monomeric structures of the CGTase exhibit five domains (A, B, C, D, and E domains) with different molecular weights and amino acid sequences depending on the source. Among bacteria, Bacillus genus covers approximately 90% of the CGTase producers, while other genera like Klebsiella, Paenibacillus, and Thermoanaerobacter also shown decent contributions in recent studies. CGTase production is highly supported by alkaliphilic bacteria under submerged fermentation rather than solid-state fermentation. The bacterial sources, biochemical properties, production conditions, and structure of CGTases are compiled in this review. Cyclodextrins have the unique property of making inclusion complexes with various compounds, hence widely used in the food, pharmaceutical, cosmetics, laundry, and chemical sectors. This review presents a comprehensive view of CGTase produced by Bacillus spp., and other bacterial genera like Klebsiella, Paenibacillus, and Microbacterium. It also gives insight of the properties and recent biotechnological applications of cyclodextrins. KEY POINTS: • Transglycosylation reactions catalyzed by CGTase and their structural properties. • Comparative data of CGTase production by various genera and Bacillus spp. • Structures, properties, and applications of different cyclodextrins.
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Affiliation(s)
- Dimple S Pardhi
- Department of Microbiology and Biotechnology, University School of Sciences, Gujarat University, Ahmedabad, 380009, Gujarat, India
| | - Khushbu J Rabadiya
- Department of Microbiology and Biotechnology, University School of Sciences, Gujarat University, Ahmedabad, 380009, Gujarat, India
| | - Rakeshkumar R Panchal
- Department of Microbiology and Biotechnology, University School of Sciences, Gujarat University, Ahmedabad, 380009, Gujarat, India
| | - Vikram H Raval
- Department of Microbiology and Biotechnology, University School of Sciences, Gujarat University, Ahmedabad, 380009, Gujarat, India
| | - Rushikesh G Joshi
- Department of Biochemistry and Forensic Science, University School of Sciences, Gujarat University, Ahmedabad, 380009, Gujarat, India
| | - Kiransinh N Rajput
- Department of Microbiology and Biotechnology, University School of Sciences, Gujarat University, Ahmedabad, 380009, Gujarat, India.
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A De Novo Optimized Cell-Free System for the Expression of Soluble and Active Human Tumor Necrosis Factor-Alpha. BIOLOGY 2022; 11:biology11020157. [PMID: 35205024 PMCID: PMC8868817 DOI: 10.3390/biology11020157] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 01/14/2022] [Accepted: 01/17/2022] [Indexed: 11/27/2022]
Abstract
Simple Summary As a result of increasing demand for the pleiotropic cytokine TNF-α, recombinant human TNF-α protein with appropriate bioactivities was produced in several heterologous in vivo expression systems. While in vivo expression of this cytokine is laborious and lengthy, cell-free or in vitro expression system has the benefits of speed, simplicity, flexibility, focus of all the system energy on target protein synthesis alone, besides high soluble and functional protein yield. Therefore, we employed and optimized an E. coli-based cell-free system for the first time to express recombinant human TNF-α. Our findings revealed that cell-free expression system can be an alternative platform for producing soluble and functionally active recombinant TNF-α with a yield of 390 µg/mL in only 2 h at a temperature of 40 °C for further research and clinical trials. Abstract Cell-free (in vitro) expression is a robust alternative platform to the cell-based (in vivo) system for recombinant protein production. Tumor necrosis factor-alpha (TNF-α) is an effective pro-inflammatory cytokine with pleiotropic effects. The aim of the current study was de novo optimized expression of soluble and active human TNF-α by an in vitro method in an E. coli-based cell-free protein synthesis (CFPS) system and its biological activity evaluation. The codon-optimized synthetic human TNF-α gene was constructed by a two-step PCR, cloned into pET101/D-TOPO vector and then expressed by the E. coli CFPS system. Cell-free expression of the soluble protein was optimized using a response surface methodology (RSM). The anticancer activity of purified human TNF-α was assessed against three human cancer cell lines: Caco-2, HepG-2 and MCF-7. Data from RSM revealed that the lowest value (7.2 µg/mL) of cell-free production of recombinant human TNF-α (rhTNF-α) was obtained at a certain incubation time (6 h) and incubation temperature (20 °C), while the highest value (350 µg/mL) was recorded at 4 h and 35 °C. This rhTNF-α showed a significant anticancer potency. Our findings suggest a cell-free expression system as an alternative platform for producing soluble and functionally active recombinant TNF-α for further research and clinical trials.
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Nakapong S, Tumhom S, Kaulpiboon J, Pongsawasdi P. Heterologous expression of 4α-glucanotransferase: overproduction and properties for industrial applications. World J Microbiol Biotechnol 2022; 38:36. [PMID: 34993677 DOI: 10.1007/s11274-021-03220-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 12/20/2021] [Indexed: 12/28/2022]
Abstract
4α-Glucanotransferase (4α-GTase) is unique in its ability to form cyclic oligosaccharides, some of which are of industrial importance. Generally, low amount of enzymes is produced by or isolated from their natural sources: animals, plants, and microorganisms. Heterologous expressions of these enzymes, in an attempt to increase their production for applicable uses, have been widely studied since 1980s; however, the expressions are mostly performed in the prokaryotic bacteria, mostly Escherichia coli. Site-directed mutagenesis has added more value to these expressed enzymes to display the desired properties beneficial for their applications. The search for further suitable properties for food application leads to an extended research in expression by another group of host organism, the generally-recognized as safe host including the Bacillus and the eukaryotic yeast systems. Herein, our review focuses on two types of 4α-GTase: the cyclodextrin glycosyltransferase and amylomaltase. The updated studies on the general structure and properties of the two enzymes with emphasis on heterologous expression, mutagenesis for property improvement, and their industrial applications are provided.
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Affiliation(s)
- Santhana Nakapong
- Department of Chemistry, Faculty of Science, Ramkhamhaeng University, Bangkok, 10240, Thailand
| | - Suthipapun Tumhom
- Office of National Higher Education Science Research and Innovation Policy Council, Ministry of Higher Education Science Research and Innovation, Bangkok, 10330, Thailand
| | - Jarunee Kaulpiboon
- Division of Biochemistry, Department of Preclinical Science, Faculty of Medicine, Thammasat University, Pathumthani, 12120, Thailand.
| | - Piamsook Pongsawasdi
- Department of Biochemistry, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand.
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Kant Bhatia S, Vivek N, Kumar V, Chandel N, Thakur M, Kumar D, Yang YH, Pugazendhi A, Kumar G. Molecular biology interventions for activity improvement and production of industrial enzymes. BIORESOURCE TECHNOLOGY 2021; 324:124596. [PMID: 33440311 DOI: 10.1016/j.biortech.2020.124596] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 12/16/2020] [Accepted: 12/18/2020] [Indexed: 06/12/2023]
Abstract
Metagenomics and directed evolution technology have brought a revolution in search of novel enzymes from extreme environment and improvement of existing enzymes and tuning them towards certain desired properties. Using advanced tools of molecular biology i.e. next generation sequencing, site directed mutagenesis, fusion protein, surface display, etc. now researchers can engineer enzymes for improved activity, stability, and substrate specificity to meet the industrial demand. Although many enzymatic processes have been developed up to industrial scale, still there is a need to overcome limitations of maintaining activity during the catalytic process. In this article recent developments in enzymes industrial applications and advancements in metabolic engineering approaches to improve enzymes efficacy and production are reviewed.
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Affiliation(s)
- Shashi Kant Bhatia
- Department of Biological Engineering, College of Engineering, Konkuk University, Seoul 05029, Republic of Korea; Institute for Ubiquitous Information Technology and Application, Konkuk University, Seoul 05029, Republic of Korea
| | - Narisetty Vivek
- Centre for Climate and Environmental Protection, School of Water, Energy and Environment, Cranfield University, Cranfield MK43 0AL, UK
| | - Vinod Kumar
- Centre for Climate and Environmental Protection, School of Water, Energy and Environment, Cranfield University, Cranfield MK43 0AL, UK
| | - Neha Chandel
- School of Medical and Allied Sciences, GD Goenka University, Gurugram 122103, Haryana, India
| | - Meenu Thakur
- Department of Biotechnology, Shoolini Institute of Life Sciences and Business Management, Solan 173212, Himachal Pradesh, India
| | - Dinesh Kumar
- School of Bioengineering & Food Technology, Shoolini University of Biotechnology and Management Sciences, Solan 173229, Himachal Pradesh, India
| | - Yung-Hun Yang
- Department of Biological Engineering, College of Engineering, Konkuk University, Seoul 05029, Republic of Korea; Institute for Ubiquitous Information Technology and Application, Konkuk University, Seoul 05029, Republic of Korea
| | - Arivalagan Pugazendhi
- Innovative Green Product Synthesis and Renewable Environment Development Research Group, Faculty of Environment and Labour Safety, Ton Duc Thang University, Ho ChiMinh City, Viet Nam
| | - Gopalakrishnan Kumar
- Institute of Chemistry, Bioscience and Environmental Engineering, Faculty of Science and Technology, University of Stavanger, Box 8600 Forus, 4036 Stavanger, Norway; School of Civil and Environmental Engineering, Yonsei University, Seoul 03722, Republic of Korea.
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Kastenhofer J, Rajamanickam V, Libiseller-Egger J, Spadiut O. Monitoring and control of E. coli cell integrity. J Biotechnol 2021; 329:1-12. [PMID: 33485861 DOI: 10.1016/j.jbiotec.2021.01.009] [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: 09/11/2020] [Revised: 01/06/2021] [Accepted: 01/08/2021] [Indexed: 12/15/2022]
Abstract
Soluble expression of recombinant proteins in E. coli is often done by translocation of the product across the inner membrane (IM) into the periplasm, where it is retained by the outer membrane (OM). While the integrity of the IM is strongly coupled to viability and impurity release, a decrease in OM integrity (corresponding to increased "leakiness") leads to accumulation of product in the extracellular space, strongly impacting the downstream process. Whether leakiness is desired or not, differential monitoring and control of IM and OM integrity are necessary for an efficient E. coli bioprocess in compliance with the guidelines of Quality by Design and Process Analytical Technology. In this review, we give an overview of relevant monitoring tools, summarize the research on factors affecting E. coli membrane integrity and provide a brief discussion on how the available monitoring technology can be implemented in real-time control of E. coli cultivations.
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Affiliation(s)
- Jens Kastenhofer
- TU Wien, Institute of Chemical, Environmental and Bioscience Engineering, Research Division Biochemical Engineering, Research Group Integrated Bioprocess Development, Gumpendorfer Strasse 1a, 1060, Vienna, Austria
| | - Vignesh Rajamanickam
- TU Wien, Institute of Chemical, Environmental and Bioscience Engineering, Research Division Biochemical Engineering, Research Group Integrated Bioprocess Development, Gumpendorfer Strasse 1a, 1060, Vienna, Austria
| | - Julian Libiseller-Egger
- TU Wien, Institute of Chemical, Environmental and Bioscience Engineering, Research Division Biochemical Engineering, Research Group Integrated Bioprocess Development, Gumpendorfer Strasse 1a, 1060, Vienna, Austria
| | - Oliver Spadiut
- TU Wien, Institute of Chemical, Environmental and Bioscience Engineering, Research Division Biochemical Engineering, Research Group Integrated Bioprocess Development, Gumpendorfer Strasse 1a, 1060, Vienna, Austria.
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Enhanced Heterologous Production of Glycosyltransferase UGT76G1 by Co-Expression of Endogenous prpD and malK in Escherichia coli and Its Transglycosylation Application in Production of Rebaudioside. Int J Mol Sci 2020; 21:ijms21165752. [PMID: 32796599 PMCID: PMC7460871 DOI: 10.3390/ijms21165752] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 08/06/2020] [Accepted: 08/10/2020] [Indexed: 02/06/2023] Open
Abstract
Steviol glycosides (SGs) with zero calories and high-intensity sweetness are the best substitutes of sugar for the human diet. Uridine diphosphate dependent glycosyltransferase (UGT) UGT76G1, as a key enzyme for the biosynthesis of SGs with a low heterologous expression level, hinders its application. In this study, a suitable fusion partner, Smt3, was found to enhance the soluble expression of UGT76G1 by 60%. Additionally, a novel strategy to improve the expression of Smt3-UGT76G1 was performed, which co-expressed endogenous genes prpD and malK in Escherichia coli. Notably, this is the first report of constructing an efficient E. coli expression system by regulating prpD and malK expression, which remarkably improved the expression of Smt3-UGT76G1 by 200% as a consequence. Using the high-expression strain E. coli BL21 (DE3) M/P-3-S32U produced 1.97 g/L of Smt3-UGT76G1 with a yield rate of 61.6 mg/L/h by fed-batch fermentation in a 10 L fermenter. The final yield of rebadioside A (Reb A) and rebadioside M (Reb M) reached 4.8 g/L and 1.8 g/L, respectively, when catalyzed by Smt3-UGT76G1 in the practical UDP-glucose regeneration transformation system in vitro. This study not only carried out low-cost biotransformation of SGs but also provided a novel strategy for improving expression of heterologous proteins in E. coli.
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