1
|
Howe G, Bal M, Wasmuth M, Massaro G, Rahim AA, Ali S, Rivera M, Schofield DM, Omotosho A, Ward J, Keshavarz-Moore E, Mason C, Nesbeth DN. An autonucleolytic suspension HEK293F host cell line for high-titer serum-free AAV5 and AAV9 production with reduced levels of DNA impurity. Mol Ther Methods Clin Dev 2024; 32:101317. [PMID: 39257529 PMCID: PMC11385518 DOI: 10.1016/j.omtm.2024.101317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Accepted: 08/07/2024] [Indexed: 09/12/2024]
Abstract
We sought to engineer mammalian cells to secrete nuclease activity as a step toward removing the need to purchase commercial nucleases as process additions in bioprocessing of AAV5 and AAV9 as gene therapy vectors. Engineering HeLa cells with a serratial nuclease transgene did not bring about nuclease activity in surrounding media whereas engineering serum-free, suspension-adapted HEK293F cells with a staphylococcal nuclease transgene did result in detectable nuclease activity in surrounding media of the resultant stable transfectant cell line, "NuPro-1S." When cultivated in serum-free media, NuPro-1S cells yielded 3.06 × 1010 AAV5 viral genomes (vg)/mL via transient transfection, compared with 3.85 × 109 vg/mL from the parental HEK293F cell line. AAV9 production, followed by purification by ultracentrifugation, yielded 1.8 × 1013 vg/mL from NuPro-1S cells compared with 7.35 × 1012 vg/mL from HEK293F cells. AAV9 from both HEK293F and NuPro-1S showed almost identical ability to transduce cells embedded in a scaffold tissue mimic or cells of mouse neonate brain tissue in vivo. Comparison of agarose gel data indicated that the DNA content of AAV5 and AAV9 process streams from NuPro-1S cells was reduced by approximately 60% compared with HEK293F cells. A similar reduction in HEK293F cells was only achievable with a 50 U/mL Benzonase treatment.
Collapse
Affiliation(s)
- Geoffrey Howe
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, London WC1E 6BT, UK
| | - Mehtap Bal
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, London WC1E 6BT, UK
| | - Matt Wasmuth
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, London WC1E 6BT, UK
| | - Giulia Massaro
- UCL School of Pharmacy, University College London, London WC1N 1AX, UK
| | - Ahad A Rahim
- UCL School of Pharmacy, University College London, London WC1N 1AX, UK
| | - Sadfer Ali
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, London WC1E 6BT, UK
| | - Milena Rivera
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, London WC1E 6BT, UK
| | - Desmond M Schofield
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, London WC1E 6BT, UK
| | - Aminat Omotosho
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, London WC1E 6BT, UK
| | - John Ward
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, London WC1E 6BT, UK
| | - Eli Keshavarz-Moore
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, London WC1E 6BT, UK
| | - Chris Mason
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, London WC1E 6BT, UK
| | - Darren N Nesbeth
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, London WC1E 6BT, UK
| |
Collapse
|
2
|
Ali S, Rivera M, Ward J, Keshavarz-Moore E, Mason C, Nesbeth DN. Serum-free lentiviral vector production is compatible with medium-resident nuclease activity arising from adherent HEK293T host cells engineered with a nuclease-encoding transgene. Heliyon 2023; 9:e17067. [PMID: 37484388 PMCID: PMC10361239 DOI: 10.1016/j.heliyon.2023.e17067] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 05/30/2023] [Accepted: 06/06/2023] [Indexed: 07/25/2023] Open
Abstract
At present lentiviral vector production for cell and gene therapy commonly involves transient plasmid transfection of mammalian cells cultivated in serum-containing media and addition of exogenous nuclease to reduce host cell and plasmid DNA impurities. Switching from serum-containing media to chemically-defined, serum free media, and minimising the number of process additions, are both increasingly regarded as necessary steps for simplifying and potentially automating lentiviral vector bioprocessing in future. Here we adapted human embryonic kidney 293T (HEK293T) cells to grow in serum-free media and also modified these cells with transgenes designed to encode a secreted nuclease activity. Stable transfection of HEK293T cells with transgenes encoding the Staphylococcus aureus nuclease B (NucB) open reading frame with either its native secretion signal peptide, the murine Igκ chain leader sequence or a novel viral transport fusion protein, all resulted in qualitatively detectable nuclease activity in serum-free media. Serum-free transient transfection of human embryonic kidney HEK293T cells stably harbouring the transgene for NucB with its native secretion signal produced active lentivirus in the presence of medium-resident nuclease activity. This lentivirus material was able to transduce the AGF-T immortal T cell line with a green fluorescent protein reporter payload at a level of 2.05 × 105 TU/mL (±3.34 × 104 TU/mL). Sufficient nuclease activity was present in 10 μL of this unconcentrated lentivirus material to degrade 1.5 μg DNA within 2 h at 37 °C, without agitation - conditions compatible with lentivirus production. These observations demonstrate that lentiviral vector production, by transient transfection, is compatible with host cells harbouring a nuclease transgene and evidencing nuclease activity in their surrounding growth media. This work provides a solid basis for future investigations, beyond the scope of this present study, in which commercial and academic groups can apply this approach to therapeutic payloads and potentially omit exogenous nuclease bioprocess additions.
Collapse
|
3
|
Menacho‐Melgar R, Moreb EA, Efromson JP, Yang T, Hennigan JN, Wang R, Lynch MD. Improved two‐stage protein expression and purification via autoinduction of both autolysis and auto DNA/RNA hydrolysis conferred by phage lysozyme and DNA/RNA endonuclease. Biotechnol Bioeng 2020; 117:2852-2860. [DOI: 10.1002/bit.27444] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Revised: 05/06/2020] [Accepted: 05/26/2020] [Indexed: 01/11/2023]
Affiliation(s)
| | - Eirik A. Moreb
- Department of Biomedical Engineering Duke University Durham North Carolina
| | - John P. Efromson
- Department of Biomedical Engineering Duke University Durham North Carolina
| | - Tian Yang
- Department of Biomedical Engineering Duke University Durham North Carolina
| | | | - Ruixin Wang
- Department of Biomedical Engineering Duke University Durham North Carolina
| | - Michael D. Lynch
- Department of Biomedical Engineering Duke University Durham North Carolina
| |
Collapse
|
4
|
Wang Y, Jia P, Sharif R, Li Z, Li Y, Chen P. High-Level Production of DNA-Specific Endonuclease AsEndI with Synonymous Codon and its Potential Utilization for Removing DNA Contamination. Appl Biochem Biotechnol 2017; 185:641-654. [PMID: 29250754 DOI: 10.1007/s12010-017-2672-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Accepted: 11/30/2017] [Indexed: 12/19/2022]
Abstract
Endonuclease I is a widely distributed periplasmic or extracellular enzyme. A method for the high-level production of recombinant AsEndI (endonuclease I from Aliivibrio salmonicida) in Escherichia coli with secretion expression is investigated. The coding sequence of AsEndI gene was assembled according to the E. coli codon usage bias, and AsEndI was expressed in the periplasm of E. coli TOP10 with a C-terminal 6× His-tagged fusion. The recombinant AsEndI (His-AsEndI) was purified by Ni-NTA resin with a yield of 1.29 × 107 U from 1-L LB medium. His-AsEndI could be classified into Ca2+/Mg2+-dependent nucleases and showed highest nuclease activity to dsDNA at pH 8.0 and 37 °C. His-AsEndI is highly active in a broad range of salt concentration range up to 1.0 M with optimal NaCl concentration at 0.4 M. His-AsEndI can effectively remove DNA contamination in RNA sample or in PCR reagents to the level that cannot be detected by highly sensitive nested PCR and without adverse effects on the subsequent PCR reaction. His-AsEndI can remove DNA contamination at high salt conditions, especially for the DNA that may be shielded by DNA-binding protein at low salt conditions.
Collapse
Affiliation(s)
- Yuan Wang
- College of Life Sciences, Northwest Agriculture and Forestry University, Yangling, Shaanxi, 712100, China
| | - Peng Jia
- College of Life Sciences, Northwest Agriculture and Forestry University, Yangling, Shaanxi, 712100, China
| | - Rahat Sharif
- College of Horticulture, Northwest Agriculture and Forestry University, Yangling, Shaanxi, 712100, China
| | - Zhengchen Li
- College of Life Sciences, Northwest Agriculture and Forestry University, Yangling, Shaanxi, 712100, China
| | - Yuhong Li
- College of Horticulture, Northwest Agriculture and Forestry University, Yangling, Shaanxi, 712100, China.
| | - Peng Chen
- College of Life Sciences, Northwest Agriculture and Forestry University, Yangling, Shaanxi, 712100, China.
| |
Collapse
|
5
|
Improving Fab' fragment retention in an autonucleolytic Escherichia coli strain by swapping periplasmic nuclease translocation signal from OmpA to DsbA. Biotechnol Lett 2017; 39:1865-1873. [PMID: 28875244 PMCID: PMC5674116 DOI: 10.1007/s10529-017-2425-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Accepted: 08/22/2017] [Indexed: 12/27/2022]
Abstract
Objectives To reduce unwanted Fab’ leakage from an autonucleolytic Escherichia coli strain, which co-expresses OmpA-signalled Staphylococcal nuclease and Fab’ fragment in the periplasm, by substituting in Serratial nuclease and the DsbA periplasm translocation signal as alternatives. Results We attempted to genetically fuse a nuclease from Serratia marcescens to the OmpA signal peptide but plasmid construction failed, possibly due to toxicity of the resultant nuclease. Combining Serratial nuclease to the DsbA signal peptide was successful. The strain co-expressing this nuclease and periplasmic Fab’ grew in complex media and exhibited nuclease activity detectable by DNAse agar plate but its growth in defined medium was retarded. Fab’ coexpression with Staphylococcal nuclease fused to the DsbA signal peptide resulted in cells exhibiting nuclease activity and growth in defined medium. In cultivation to high cell density in a 5 l bioreactor, DsbA-fused Staphylococcal nuclease co-expression coincided with reduced Fab’ leakage relative to the original autonucleolytic Fab’ strain with OmpA-fused staphylococcal nuclease. Conclusions We successfully rescued Fab’ leakage back to acceptable levels and established a basis for future investigation of the linkage between periplasmic nuclease expression and leakage of co-expressed periplasmic Fab’ fragment to the surrounding growth media.
Collapse
|
6
|
Borsa BA, Tuna BG, Hernandez FJ, Hernandez LI, Bayramoglu G, Arica MY, Ozalp VC. Staphylococcus aureus detection in blood samples by silica nanoparticle-oligonucleotides conjugates. Biosens Bioelectron 2016; 86:27-32. [DOI: 10.1016/j.bios.2016.06.023] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Revised: 05/27/2016] [Accepted: 06/09/2016] [Indexed: 01/01/2023]
|
7
|
Hu Y, Meng J, Shi C, Hervin K, Fratamico PM, Shi X. Characterization and comparative analysis of a second thermonuclease from Staphylococcus aureus. Microbiol Res 2013; 168:174-82. [DOI: 10.1016/j.micres.2012.09.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 09/12/2012] [Accepted: 09/14/2012] [Indexed: 12/12/2022]
|
8
|
Nesbeth DN, Perez-Pardo MA, Ali S, Ward J, Keshavarz-Moore E. Growth and productivity impacts of periplasmic nuclease expression in an Escherichia coli Fab' fragment production strain. Biotechnol Bioeng 2011; 109:517-27. [PMID: 21898368 DOI: 10.1002/bit.23316] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2011] [Revised: 08/03/2011] [Accepted: 08/17/2011] [Indexed: 11/09/2022]
Abstract
Host cell engineering is becoming a realistic option in whole bioprocess strategies to maximize product manufacturability. High molecular weight (MW) genomic DNA currently hinders bioprocessing of Escherichia coli by causing viscosity in homogenate feedstocks. We previously showed that co-expressing Staphylococcal nuclease and human Fab' fragment in the periplasm of E. coli enables auto-hydrolysis of genomic DNA upon cell disruption, with a consequent reduction in feedstock viscosity and improvement in clarification performance. Here we report the impact of periplasmic nuclease expression on stability of DNA and Fab' fragment in homogenates, host-strain growth kinetics, cell integrity at harvest and Fab' fragment productivity. Nuclease and Fab' plasmids were shown to exert comparable levels of growth burden on the host W3110 E. coli strain. Nuclease co-expression did not compromise either the growth performance or volumetric yield of the production strain. 0.5 g/L Fab' fragment (75 L scale) and 0.7 g/L (20 L scale) was achieved for both unmodified and cell-engineered production strains. Unexpectedly, nuclease-modified cells achieved maximum Fab' levels 8-10 h earlier than the original, unmodified production strain. Scale-down studies of homogenates showed that nuclease-mediated hydrolysis of high MW DNA progressed to completion within minutes of homogenization, even when homogenates were chilled on ice, with no loss of Fab' product and no need for additional co-factors or buffering.
Collapse
Affiliation(s)
- Darren N Nesbeth
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, London WC1E 7JE, UK.
| | | | | | | | | |
Collapse
|
9
|
Production and purification of staphylococcal nuclease in Lactococcus lactis using a new expression-secretion system and a pH-regulated mini-reactor. Microb Cell Fact 2010; 9:37. [PMID: 20492646 PMCID: PMC2887397 DOI: 10.1186/1475-2859-9-37] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2009] [Accepted: 05/21/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Staphylococcal (or micrococcal) nuclease or thermonuclease (SNase or Nuc) is a naturally-secreted nucleic acid degrading enzyme that participates in Staphylococcus aureus spread in the infected host. Purified Nuc protein can be used as an exogenous reagent to clear cellular extracts and improve protein purification. Here, a recombinant form of Nuc was produced and secreted in a Gram-positive host, Lactococcus lactis, and purified from the culture medium. RESULTS The gene segment corresponding to the S. aureus nuclease without its signal peptide was cloned in an expression-secretion vector. It was then fused to a lactococcal sequence encoding a signal peptide, and expressed under the control of a lactococcal promoter that is inducible by zinc starvation. An L. lactis subsp cremoris model strain (MG1363) transformed with the resulting plasmid was grown in either of two media (GM17v and CDM) that are free of animal compounds, allowing GMP (Good Manufacturing Practice) production. Induction conditions (concentration of the metal chelator EDTA and timing of addition) in small-scale pH-regulated fermentors were optimized using LacMF (Lactis Multi-Fermentor), a home-made parallel fermentation control system able to monitor 12 reactors simultaneously. Large amounts of recombinant Nuc (rNuc) were produced and secreted in both media, and rNuc was purified from GM17v medium in a single-step procedure. CONCLUSIONS In L. lactis, rNuc production and secretion were optimal after induction by 0.5 mM EDTA in small scale (200 mL) GM17v exponential phase cultures (at an OD(600) of 2), leading to a maximal protein yield of 210 mg per L of culture medium. Purified rNuc was highly active, displaying a specific activity of 2000 U/mg.
Collapse
|
10
|
Carnes AE, Hodgson CP, Luke JM, Vincent JM, Williams JA. Plasmid DNA production combining antibiotic-free selection, inducible high yield fermentation, and novel autolytic purification. Biotechnol Bioeng 2009; 104:505-15. [DOI: 10.1002/bit.22415] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
|
11
|
Balasundaram B, Nesbeth D, Ward JM, Keshavarz-Moore E, Bracewell DG. Step change in the efficiency of centrifugation through cell engineering: co-expression of Staphylococcal nuclease to reduce the viscosity of the bioprocess feedstock. Biotechnol Bioeng 2009; 104:134-42. [PMID: 19415775 DOI: 10.1002/bit.22369] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Cell engineering to enable step change improvements in bioprocessing can be directed at targets other than increasing product titer. The physical properties of the process suspension such as viscosity, for example, have a major impact on various downstream processing unit operations. The release of chromosomal DNA during homogenization of Escherichia coli and its influence on viscosity is well-recognized. In this current article we demonstrate co-expression of Staphylococcus aureus nuclease in E. coli to reduce viscosity through auto-hydrolysis of nucleic acids. Viscosity reduction of up to 75% was achieved while the particle size distribution of cell debris was maintained approximately constant (d(50) = 0.5-0.6 microm). Critically, resultant step change improvements to the clarification performance under disc-stack centrifugation conditions are shown. The cell-engineered nuclease matched or exceeded the viscosity reduction performance seen with the addition of exogenous nuclease removing the expense and validation issues associated with such additions to a bioprocess. The resultant material dramatically altered performance in scale-down mimics of continuous disc-stack centrifugation. Laboratory scale data indicated that a fourfold reduction in the settling area of a disc-stack centrifuge can be expected due to a less viscous process stream achieved through nuclease co-expression with a recombinant protein.
Collapse
Affiliation(s)
- B Balasundaram
- Department of Biochemical Engineering, The Advanced Centre for Biochemical Engineering, University College London, London, UK
| | | | | | | | | |
Collapse
|
12
|
Carnoy C, Roten CA. The dif/Xer recombination systems in proteobacteria. PLoS One 2009; 4:e6531. [PMID: 19727445 PMCID: PMC2731167 DOI: 10.1371/journal.pone.0006531] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2009] [Accepted: 06/25/2009] [Indexed: 12/12/2022] Open
Abstract
In E. coli, 10 to 15% of growing bacteria produce dimeric chromosomes during DNA replication. These dimers are resolved by XerC and XerD, two tyrosine recombinases that target the 28-nucleotide motif (dif) associated with the chromosome's replication terminus. In streptococci and lactococci, an alternative system is composed of a unique, Xer-like recombinase (XerS) genetically linked to a dif-like motif (difSL) located at the replication terminus. Preliminary observations have suggested that the dif/Xer system is commonly found in bacteria with circular chromosomes but that assumption has not been confirmed in an exhaustive analysis. The aim of the present study was to extensively characterize the dif/Xer system in the proteobacteria, since this taxon accounts for the majority of genomes sequenced to date. To that end, we analyzed 234 chromosomes from 156 proteobacterial species and showed that most species (87.8%) harbor XerC and XerD-like recombinases and a dif-related sequence which (i) is located in non-coding sequences, (ii) is close to the replication terminus (as defined by the cumulative GC skew) (iii) has a palindromic structure, (iv) is encoded by a low G+C content and (v) contains a highly conserved XerD binding site. However, not all proteobacteria display this dif/XerCD system. Indeed, a sub-group of pathogenic ε-proteobacteria (including Helicobacter sp and Campylobacter sp) harbors a different recombination system, composed of a single recombinase (XerH) which is phylogenetically distinct from the other Xer recombinases and a motif (difH) sharing homologies with difSL. Furthermore, no homologs to dif or Xer recombinases could be detected in small endosymbiont genomes or in certain bacteria with larger chromosomes like the Legionellales. This raises the question of the presence of other chromosomal deconcatenation systems in these species. Our study highlights the complexity of dif/Xer recombinase systems in proteobacteria and paves the way for systematic detection of these components in prokaryotes.
Collapse
|
13
|
Lee GH, Cooney D, Middelberg APJ, Choe WS. The economics of inclusion body processing. Bioprocess Biosyst Eng 2006; 29:73-90. [PMID: 16718467 DOI: 10.1007/s00449-006-0047-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2005] [Accepted: 01/15/2006] [Indexed: 11/25/2022]
Abstract
Many recombinant proteins are often over-expressed in host cells, such as Escherichia coli, and are found as insoluble and inactive protein aggregates known as inclusion bodies (IBs). Recently, a novel process for IB extraction and solubilisation, based on chemical extraction, has been reported. While this method has the potential to radically intensify traditional IB processing, the process economics of the new technique have yet to be reported. This study focuses on the evaluation of process economics for several IB processing schemes based on chemical extraction and/or traditional techniques. Simulations and economic analysis were conducted at various processing conditions using granulocyte macrophage-colony stimulating factor, expressed as IBs in E. coli, as a model protein. In most cases, IB processing schemes based on chemical extraction having a shorter downstream cascade demonstrated a competitive economic edge over the conventional route, validating the new process as an economically more viable alternative for IB processing.
Collapse
Affiliation(s)
- G H Lee
- Department of Chemical and Biomolecular Engineering, National University of Singapore, 10 Kent Ridge Crescent, 117576, Singapore, Singapore
| | | | | | | |
Collapse
|
14
|
|
15
|
Balan A, Schenberg ACG. A conditional suicide system forSaccharomyces cerevisiae relying on the intracellular production of theSerratia marcescens nuclease. Yeast 2005; 22:203-12. [PMID: 15704225 DOI: 10.1002/yea.1203] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
A conditional lethal system for biological containment of genetically modified strains of Saccharomyces cerevisiae is described. This suicide system is based on the intracellular production of the Serratia marcescens nuclease in the yeast cell, aiming at the destruction of the host genetic material. The S. marcescens nuclease, encoded by the nucA gene, is normally secreted by the bacterium into the medium. In the present work, the nucA gene, devoid of its signal peptide coding sequence, was cloned in a yeast expression vector, under control of the glucose-repressed S. cerevisiae alcohol dehydrogenase 2 gene (ADH2) promoter. When transformed into S. cerevisiae, the recombinant plasmid proved to be effective in killing the host cells upon glucose depletion from the medium, and the nuclease activity was found in lysates prepared from the transformants. In addition, the nuclease degrading effect was shown to reach chromosomal DNA in the yeast host. The killing effect of the nucA plasmid was also demonstrated in soil microcosm assays, indicating that whenever the GMM escapes into the environment where glucose is scarce, the nucA gene will be expressed and the resulting nuclease will destroy the genetic material and kill the cells. In contrast to other suicide systems that target the cell envelope, the advantage of the one described here is that it disfavours horizontal gene transfer from recombinant yeast cells to other microorganisms found in the environment.
Collapse
Affiliation(s)
- Andrea Balan
- Universidade de São Paulo, Instituto de Ciências Biomédicas, Departamento de Microbiologia, Avenida Professor Lineu Prestes 1374, São Paulo 05508-900, SP, Brasil
| | | |
Collapse
|
16
|
Tin Lee C, Morreale G, Middelberg APJ. Combined in-fermenter extraction and cross-flow microfiltration for improved inclusion body processing. Biotechnol Bioeng 2003; 85:103-13. [PMID: 14705017 DOI: 10.1002/bit.10878] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
In this study we demonstrate a new in-fermenter chemical extraction procedure that degrades the cell wall of Escherichia coli and releases inclusion bodies (IBs) into the fermentation medium. We then prove that cross-flow microfiltration can be used to remove 91% of soluble contaminants from the released IBs. The extraction protocol, based on a combination of Triton X-100, EDTA, and intracellular T7 lysozyme, effectively released most of the intracellular soluble content without solubilising the IBs. Cross-flow microfiltration using a 0.2 microm ceramic membrane successfully recovered the granulocyte macrophage-colony stimulating factor (GM-CSF) IBs with removal of 91% of the soluble contaminants and virtually no loss of IBs to the permeate. The filtration efficiency, in terms of both flux and transmission, was significantly enhanced by in-fermenter Benzonase digestion of nucleic acids following chemical extraction. Both the extraction and filtration methods exerted their efficacy directly on a crude fermentation broth, eliminating the need for cell recovery and resuspension in buffer. The processes demonstrated here can all be performed using just a fermenter and a single cross-flow filtration unit, demonstrating a high level of process intensification. Furthermore, there is considerable scope to also use the microfiltration system to subsequently solubilise the IBs, to separate the denatured protein from cell debris, and to refold the protein using diafiltration. In this way refolded protein can potentially be obtained, in a relatively pure state, using only two unit operations.
Collapse
Affiliation(s)
- Chew Tin Lee
- Department of Chemical Engineering, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, United Kingdom
| | | | | |
Collapse
|