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Bolaños-Martínez OC, Mahendran G, Rosales-Mendoza S, Vimolmangkang S. Current Status and Perspective on the Use of Viral-Based Vectors in Eukaryotic Microalgae. Mar Drugs 2022; 20:md20070434. [PMID: 35877728 PMCID: PMC9318342 DOI: 10.3390/md20070434] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 06/25/2022] [Accepted: 06/27/2022] [Indexed: 11/29/2022] Open
Abstract
During the last two decades, microalgae have attracted increasing interest, both commercially and scientifically. Commercial potential involves utilizing valuable natural compounds, including carotenoids, polysaccharides, and polyunsaturated fatty acids, which are widely applicable in food, biofuel, and pharmaceutical industries. Conversely, scientific potential focuses on bioreactors for producing recombinant proteins and developing viable technologies to significantly increase the yield and harvest periods. Here, viral-based vectors and transient expression strategies have significantly contributed to improving plant biotechnology. We present an updated outlook covering microalgal biotechnology for pharmaceutical application, transformation techniques for generating recombinant proteins, and genetic engineering tactics for viral-based vector construction. Challenges in industrial application are also discussed.
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Affiliation(s)
- Omayra C. Bolaños-Martínez
- Department of Pharmacognosy and Pharmaceutical Botany, Faculty of Pharmaceutical Sciences, Chulalongkorn University, Bangkok 10330, Thailand; (O.C.B.-M.); (G.M.)
- Center of Excellence in Plant-Produced Pharmaceuticals, Chulalongkorn University, Bangkok 10330, Thailand
| | - Ganesan Mahendran
- Department of Pharmacognosy and Pharmaceutical Botany, Faculty of Pharmaceutical Sciences, Chulalongkorn University, Bangkok 10330, Thailand; (O.C.B.-M.); (G.M.)
- Center of Excellence in Plant-Produced Pharmaceuticals, Chulalongkorn University, Bangkok 10330, Thailand
| | - Sergio Rosales-Mendoza
- Laboratorio de Biofarmacéuticos Recombinantes, Facultad de Ciencias Químicas, Universidad Autónoma de San Luis Potosí, Av. Dr. Manuel Nava 6, San Luis Potosí 78210, Mexico;
- Sección de Biotecnología, Centro de Investigación en Ciencias de la Salud y Biomedicina, Universidad Autónoma de San Luis Potosí, Av. Sierra Leona 550, Lomas 2a Sección, San Luis Potosí 78210, Mexico
| | - Sornkanok Vimolmangkang
- Department of Pharmacognosy and Pharmaceutical Botany, Faculty of Pharmaceutical Sciences, Chulalongkorn University, Bangkok 10330, Thailand; (O.C.B.-M.); (G.M.)
- Center of Excellence in Plant-Produced Pharmaceuticals, Chulalongkorn University, Bangkok 10330, Thailand
- Correspondence: ; Tel.: +662-218-8358
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Grama SB, Liu Z, Li J. Emerging Trends in Genetic Engineering of Microalgae for Commercial Applications. Mar Drugs 2022; 20:285. [PMID: 35621936 PMCID: PMC9143385 DOI: 10.3390/md20050285] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 04/15/2022] [Accepted: 04/19/2022] [Indexed: 02/04/2023] Open
Abstract
Recently, microalgal biotechnology has received increasing interests in producing valuable, sustainable and environmentally friendly bioproducts. The development of economically viable production processes entails resolving certain limitations of microalgal biotechnology, and fast evolving genetic engineering technologies have emerged as new tools to overcome these limitations. This review provides a synopsis of recent progress, current trends and emerging approaches of genetic engineering of microalgae for commercial applications, including production of pharmaceutical protein, lipid, carotenoids and biohydrogen, etc. Photochemistry improvement in microalgae and CO2 sequestration by microalgae via genetic engineering were also discussed since these subjects are closely entangled with commercial production of the above mentioned products. Although genetic engineering of microalgae is proved to be very effective in boosting performance of production in laboratory conditions, only limited success was achieved to be applicable to industry so far. With genetic engineering technologies advancing rapidly and intensive investigations going on, more bioproducts are expected to be produced by genetically modified microalgae and even much more to be prospected.
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Affiliation(s)
- Samir B. Grama
- Laboratory of Natural Substances, Biomolecules and Biotechnological Applications, University of Oum El Bouaghi, Oum El Bouaghi 04000, Algeria;
| | - Zhiyuan Liu
- College of Marine Sciences, Hainan University, Haikou 570228, China;
| | - Jian Li
- College of Agricultural Sciences, Panzhihua University, Panzhihua 617000, China
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3
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Ramos-Vega A, Angulo C, Bañuelos-Hernández B, Monreal-Escalante E. Microalgae-made vaccines against infectious diseases. ALGAL RES 2021. [DOI: 10.1016/j.algal.2021.102408] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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4
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de Grahl I, Reumann S. Stramenopile microalgae as "green biofactories" for recombinant protein production. World J Microbiol Biotechnol 2021; 37:163. [PMID: 34453200 PMCID: PMC8397651 DOI: 10.1007/s11274-021-03126-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Accepted: 08/06/2021] [Indexed: 12/23/2022]
Abstract
Photoautotrophic microalgae have become intriguing hosts for recombinant protein production because they offer important advantages of both prokaryotic and eukaryotic expression systems. Advanced molecular tools have recently been established for the biotechnologically relevant group of stramenopile microalgae, particularly for several Nannochloropsis species and diatoms. Strategies for the selection of powerful genetic elements and for optimization of protein production have been reported. Much needed high-throughput techniques required for straight-forward identification and selection of the best expression constructs and transformants have become available and are discussed. The first recombinant proteins have already been produced successfully in stramenopile microalgae and include not only several subunit vaccines but also one antimicrobial peptide, a fish growth hormone, and an antibody. These research results offer interesting future applications in aquaculture and as biopharmaceuticals. In this review we highlight recent progress in genetic technology development for recombinant protein production in the most relevant Nannochloropsis species and diatoms. Diverse realistic biotechnological applications of these proteins are emphasized that have the potential to establish stramenopile algae as sustainable green factories for an economically competitive production of high-value biomolecules.
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Affiliation(s)
- Imke de Grahl
- Plant Biochemistry and Infection Biology, Institute of Plant Science and Microbiology, Universität Hamburg, Ohnhorststr. 18, 22609, Hamburg, Germany.
| | - Sigrun Reumann
- Plant Biochemistry and Infection Biology, Institute of Plant Science and Microbiology, Universität Hamburg, Ohnhorststr. 18, 22609, Hamburg, Germany
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Shahin K, Pirezan F, Rogge M, LaFrentz BR, Shrestha RP, Hildebrand M, Lu F, HogenEsch H, Soto E. Development of IglC and GroEL recombinant vaccines for francisellosis in Nile tilapia, Oreochromis niloticus. FISH & SHELLFISH IMMUNOLOGY 2020; 105:341-349. [PMID: 32712230 DOI: 10.1016/j.fsi.2020.07.045] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 07/14/2020] [Accepted: 07/21/2020] [Indexed: 06/11/2023]
Abstract
Warm-water piscine francisellosis is a granulomatous bacterial disease caused by Francisella orientalis (Fo). The disease has been detected in a wide range of fish species globally, causing mortalities as high as 90% and significant economic losses. Currently there are no commercially available vaccines and few treatment options exist. In the current study, two novel recombinant vaccines were prepared using diatom-expressed IglC or bacterial-expressed GroEL proteins. The vaccine antigens were emulsified with either nanoparticles or a commercially available oil-based adjuvant. Nile tilapia, Oreochromis niloticus, fingerlings were immunized intracoelomically with the recombinant IglC or GroEL vaccines, diatoms alone or phosphate buffer saline. Approximately 840-degree days post-vaccination, fish were challenged via immersion with 106 CFU/mL of wild-type Fo. Twenty-one days post challenge (dpc), the highest relative percent survival was recorded in the IglC-Montanide group (75%), compared to 53%, 50%, 22%, 19% and 16% in the IglC-nanoparticles, GroEL-Montanide, GroEL-nanoparticles, diatoms-Montanide and diatoms-nanoparticles groups, respectively. Protection correlated with significantly higher specific antibody responses in the IglC-Montanide group. Moreover, a significantly lower bacterial load was detected in spleen samples from the IglC-Montanide survivor tilapia compared to the other experimental groups. This is the first report of recombinant vaccines against piscine francisellosis in tilapia. The Fo vaccines described in our study may facilitate development of a safe, cost-effective and highly protective vaccine against francisellosis in farmed tilapia.
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Affiliation(s)
- Khalid Shahin
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California Davis, 95616, Davis, CA, USA
| | - Felipe Pirezan
- Department of Veterinary Clinics and Surgery, School of Veterinary Medicine, Federal University of Minas Gerais, 31270-901, Belo Horizonte, MG, Brazil
| | - Matt Rogge
- Department of Biology, University of Wisconsin-Stevens Point, Stevens Point, WI, USA
| | | | - Roshan P Shrestha
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA
| | - Mark Hildebrand
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA
| | - Fangjia Lu
- Department of Comparative Pathobiology, College of Veterinary Medicine, Purdue University, West Lafayette, IN, 47907, USA
| | - Harm HogenEsch
- Department of Comparative Pathobiology, College of Veterinary Medicine, Purdue University, West Lafayette, IN, 47907, USA
| | - Esteban Soto
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California Davis, 95616, Davis, CA, USA.
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Kadono T, Tomaru Y, Suzuki K, Yamada K, Adachi M. The possibility of using marine diatom-infecting viral promoters for the engineering of marine diatoms. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2020; 296:110475. [PMID: 32540005 DOI: 10.1016/j.plantsci.2020.110475] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2019] [Revised: 02/26/2020] [Accepted: 03/18/2020] [Indexed: 06/11/2023]
Abstract
Marine diatoms constitute a major group of unicellular photosynthetic eukaryotes. Diatoms are widely applicable for both basic studies and applied studies. Molecular tools and techniques have been developed for diatom research. Among these tools, several endogenous gene promoters (e.g., the fucoxanthin chlorophyll a/c-binding protein gene promoter) have become available for expressing transgenes in diatoms. Gene promoters that drive transgene expression at a high level are very important for the metabolic engineering of diatoms. Various marine diatom-infecting viruses (DIVs), including both DNA viruses and RNA viruses, have recently been isolated, and their genome sequences have been characterized. Promoters from viruses that infect plants and mammals are widely used as constitutive promoters to achieve high expression of transgenes. Thus, we recently investigated the activity of promoters derived from marine DIVs in the marine diatom, Phaeodactylum tricornutum. We discuss novel viral promoters that will be useful for the future metabolic engineering of diatoms.
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Affiliation(s)
- Takashi Kadono
- Laboratory of Aquatic Environmental Science, Faculty of Agriculture and Marine Science, Kochi University, Otsu-200, Monobe, Nankoku, Kochi, 783-8502, Japan
| | - Yuji Tomaru
- National Research Institute of Fisheries and Environment of Inland Sea, Japan Fisheries Research and Education Agency, 2-17-5 Maruishi, Hatsukaichi, Hiroshima, 739-0452, Japan
| | - Kengo Suzuki
- euglena Co., Ltd., G-BASE Tamachi 2nd and 3rd Floor 5-29-11 Shiba Minato-ku, Tokyo, 108-0014, Japan
| | - Koji Yamada
- euglena Co., Ltd., G-BASE Tamachi 2nd and 3rd Floor 5-29-11 Shiba Minato-ku, Tokyo, 108-0014, Japan
| | - Masao Adachi
- Laboratory of Aquatic Environmental Science, Faculty of Agriculture and Marine Science, Kochi University, Otsu-200, Monobe, Nankoku, Kochi, 783-8502, Japan.
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Rosales-Mendoza S, Solís-Andrade KI, Márquez-Escobar VA, González-Ortega O, Bañuelos-Hernandez B. Current advances in the algae-made biopharmaceuticals field. Expert Opin Biol Ther 2020; 20:751-766. [DOI: 10.1080/14712598.2020.1739643] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Sergio Rosales-Mendoza
- Facultad de Ciencias Químicas, Universidad Autónoma de San Luis Potosí, San Luis Potosí, México
- Sección de Biotecnología, Centro de Investigación en Ciencias de la Salud y Biomedicina, Universidad Autónoma de San Luis Potosí, San Luis Potosí, México
| | - Karla I. Solís-Andrade
- Facultad de Ciencias Químicas, Universidad Autónoma de San Luis Potosí, San Luis Potosí, México
- Sección de Biotecnología, Centro de Investigación en Ciencias de la Salud y Biomedicina, Universidad Autónoma de San Luis Potosí, San Luis Potosí, México
| | - Verónica A. Márquez-Escobar
- Facultad de Ciencias Químicas, Universidad Autónoma de San Luis Potosí, San Luis Potosí, México
- Sección de Biotecnología, Centro de Investigación en Ciencias de la Salud y Biomedicina, Universidad Autónoma de San Luis Potosí, San Luis Potosí, México
| | - Omar González-Ortega
- Facultad de Ciencias Químicas, Universidad Autónoma de San Luis Potosí, San Luis Potosí, México
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Falciatore A, Jaubert M, Bouly JP, Bailleul B, Mock T. Diatom Molecular Research Comes of Age: Model Species for Studying Phytoplankton Biology and Diversity. THE PLANT CELL 2020; 32:547-572. [PMID: 31852772 PMCID: PMC7054031 DOI: 10.1105/tpc.19.00158] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 10/18/2019] [Accepted: 12/13/2019] [Indexed: 05/08/2023]
Abstract
Diatoms are the world's most diverse group of algae, comprising at least 100,000 species. Contributing ∼20% of annual global carbon fixation, they underpin major aquatic food webs and drive global biogeochemical cycles. Over the past two decades, Thalassiosira pseudonana and Phaeodactylum tricornutum have become the most important model systems for diatom molecular research, ranging from cell biology to ecophysiology, due to their rapid growth rates, small genomes, and the cumulative wealth of associated genetic resources. To explore the evolutionary divergence of diatoms, additional model species are emerging, such as Fragilariopsis cylindrus and Pseudo-nitzschia multistriata Here, we describe how functional genomics and reverse genetics have contributed to our understanding of this important class of microalgae in the context of evolution, cell biology, and metabolic adaptations. Our review will also highlight promising areas of investigation into the diversity of these photosynthetic organisms, including the discovery of new molecular pathways governing the life of secondary plastid-bearing organisms in aquatic environments.
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Affiliation(s)
- Angela Falciatore
- Institut de Biologie Physico-Chimique, Laboratory of Chloroplast Biology and Light Sensing in Microalgae, UMR7141 Centre National de la Recherche Scientifique (CNRS), Sorbonne Université, 75005 Paris, France
- Institut de Biologie Paris-Seine, Laboratory of Computational and Quantitative Biology, UMR7238 Sorbonne Université, 75005 Paris, France
| | - Marianne Jaubert
- Institut de Biologie Physico-Chimique, Laboratory of Chloroplast Biology and Light Sensing in Microalgae, UMR7141 Centre National de la Recherche Scientifique (CNRS), Sorbonne Université, 75005 Paris, France
- Institut de Biologie Paris-Seine, Laboratory of Computational and Quantitative Biology, UMR7238 Sorbonne Université, 75005 Paris, France
| | - Jean-Pierre Bouly
- Institut de Biologie Physico-Chimique, Laboratory of Chloroplast Biology and Light Sensing in Microalgae, UMR7141 Centre National de la Recherche Scientifique (CNRS), Sorbonne Université, 75005 Paris, France
- Institut de Biologie Paris-Seine, Laboratory of Computational and Quantitative Biology, UMR7238 Sorbonne Université, 75005 Paris, France
| | - Benjamin Bailleul
- Institut de Biologie Physico-Chimique, Laboratory of Chloroplast Biology and Light Sensing in Microalgae, UMR7141 Centre National de la Recherche Scientifique (CNRS), Sorbonne Université, 75005 Paris, France
| | - Thomas Mock
- School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, United Kingdom
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9
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Novel endogenous promoters for genetic engineering of the marine microalga Nannochloropsis gaditana CCMP526. ALGAL RES 2019. [DOI: 10.1016/j.algal.2019.101708] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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10
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Abstract
Microalgae are unicellular organisms that act as the crucial primary producers all over the world, typically found in marine and freshwater environments. Most of them can live photo-autotrophically, reproduce rapidly, and accumulate biomass in a short period efficiently. To adapt to the uninterrupted change of the environment, they evolve and differentiate continuously. As a result, some of them evolve special abilities such as toleration of extreme environment, generation of sophisticated structure to adapt to the environment, and avoid predators. Microalgae are believed to be promising bioreactors because of their high lipid and pigment contents. Genetic engineering technologies have given revolutions in the microalgal industry, which decoded the secrets of microalgal genes, express recombinant genes in microalgal genomes, and largely soar the accumulation of interested components in transgenic microalgae. However, owing to several obstructions, the industry of transgenic microalgae is still immature. Here, we provide an overview to emphasize the advantage and imperfection of the existing transgenic microalgal bioreactors.
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Affiliation(s)
- Zhi-Cong Liang
- College of Food Science and Engineering, South China University of Technology, Guangzhou, China
| | - Ming-Hua Liang
- College of Food Science and Engineering, South China University of Technology, Guangzhou, China
| | - Jian-Guo Jiang
- College of Food Science and Engineering, South China University of Technology, Guangzhou, China
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Jaramillo-Madrid AC, Ashworth J, Fabris M, Ralph PJ. Phytosterol biosynthesis and production by diatoms (Bacillariophyceae). PHYTOCHEMISTRY 2019; 163:46-57. [PMID: 31005802 DOI: 10.1016/j.phytochem.2019.03.018] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 03/22/2019] [Accepted: 03/22/2019] [Indexed: 06/09/2023]
Abstract
Diatoms are abundant unicellular marine photosynthetic algae that have genetically diversified their physiology and metabolism while adapting to numerous environments. The metabolic repertoire of diatoms presents opportunities to characterise the biosynthesis and production of new and potentially valuable microalgal compounds, including sterols. Sterols of plant origin, known as phytosterols, have been studied for health benefits including demonstrated cholesterol-lowering properties. In this review we summarise sterol diversity, the unique metabolic features of sterol biosynthesis in diatoms, and prospects for the extraction of diatom phytosterols in comparison to existing sources. We also review biotechnological efforts to manipulate diatom biosynthesis, including culture conditions and avenues for the rational engineering of metabolism and cellular regulation.
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Affiliation(s)
| | - Justin Ashworth
- Climate Change Cluster, University of Technology Sydney, Sydney, Australia.
| | - Michele Fabris
- Climate Change Cluster, University of Technology Sydney, Sydney, Australia; CSIRO Synthetic Biology Future Science Platform, PO Box 2583, Brisbane, QLD, 4001, Australia
| | - Peter J Ralph
- Climate Change Cluster, University of Technology Sydney, Sydney, Australia.
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12
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Ramos-Vega A, Rosales-Mendoza S, Bañuelos-Hernández B, Angulo C. Prospects on the Use of Schizochytrium sp. to Develop Oral Vaccines. Front Microbiol 2018; 9:2506. [PMID: 30410471 PMCID: PMC6209683 DOI: 10.3389/fmicb.2018.02506] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Accepted: 10/02/2018] [Indexed: 12/12/2022] Open
Abstract
Although oral subunit vaccines are highly relevant in the fight against widespread diseases, their high cost, safety and proper immunogenicity are attributes that have yet to be addressed in many cases and thus these limitations should be considered in the development of new oral vaccines. Prominent examples of new platforms proposed to address these limitations are plant cells and microalgae. Schizochytrium sp. constitutes an attractive expression host for vaccine production because of its high biosynthetic capacity, fast growth in low cost culture media, and the availability of processes for industrial scale production. In addition, whole Schizochytrium sp. cells may serve as delivery vectors; especially for oral vaccines since Schizochytrium sp. is safe for oral consumption, produces immunomodulatory compounds, and may provide bioencapsulation to the antigen, thus increasing its bioavailability. Remarkably, Schizochytrium sp. was recently used for the production of a highly immunoprotective influenza vaccine. Moreover, an efficient method for transient expression of antigens based on viral vectors and Schizochytrium sp. as host has been recently developed. In this review, the potential of Schizochytrium sp. in vaccinology is placed in perspective, with emphasis on its use as an attractive oral vaccination vehicle.
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Affiliation(s)
- Abel Ramos-Vega
- Grupo de Inmunología and Vacunología, Centro de Investigaciones Biológicas del Noroeste, La Paz, Mexico
| | - Sergio Rosales-Mendoza
- Laboratorio de Biofarmacéuticos Recombinantes, Facultad de Ciencias Químicas, Universidad Autónoma de San Luis Potosí, San Luis Potosí, Mexico.,Sección de Biotecnología, Centro de Investigación en Ciencias de la Salud y Biomedicina, Universidad Autónoma de San Luis Potosí, San Luis Potosí, Mexico
| | | | - Carlos Angulo
- Grupo de Inmunología and Vacunología, Centro de Investigaciones Biológicas del Noroeste, La Paz, Mexico
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13
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Shrestha RP, Hildebrand M. Development of a silicon limitation inducible expression system for recombinant protein production in the centric diatoms Thalassiosira pseudonana and Cyclotella cryptica. Microb Cell Fact 2017; 16:145. [PMID: 28818078 PMCID: PMC5561644 DOI: 10.1186/s12934-017-0760-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 08/10/2017] [Indexed: 01/03/2023] Open
Abstract
Background An inducible promoter for recombinant protein expression provides substantial benefits because under induction conditions cellular energy and metabolic capability can be directed into protein synthesis. The most widely used inducible promoter for diatoms is for nitrate reductase, however, nitrogen metabolism is tied into diverse aspects of cellular function, and the induction response is not necessarily robust. Silicon limitation offers a means to eliminate energy and metabolic flux into cell division processes, with little other detrimental effect on cellular function, and a protein expression system that works under those conditions could be advantageous. Results In this study, we evaluate a number of promoters for recombinant protein expression induced by silicon limitation and repressed by the presence of silicon in the diatoms Thalassiosira pseudonana and Cyclotella cryptica. In addition to silicon limitation, we describe additional strategies to elevate recombinant protein expression level, including inclusion of the 5′ fragment of the coding region of the native gene and reducing carbon flow into ancillary processes of pigment synthesis and formation of photosynthetic storage products. We achieved yields of eGFP to 1.8% of total soluble protein in C. cryptica, which is about 3.6-fold higher than that obtained with chloroplast expression and ninefold higher than nuclear expression in another well-established algal system. Conclusions Our studies demonstrate that the combination of inducible promoter and other strategies can result in robust expression of recombinant protein in a nuclear-based expression system in diatoms under silicon limited conditions, separating the protein expression regime from growth processes and improving overall recombinant protein yields. Electronic supplementary material The online version of this article (doi:10.1186/s12934-017-0760-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Roshan P Shrestha
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA
| | - Mark Hildebrand
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA.
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