Plasmid DNA primary recovery from E. coli lysates by depth bed microfiltration

From Bioreactor to Bulk Rheology: Achieving Scalable Production of Highly Concentrated Circular DNA

DNA serves as a model system in polymer physics due to its ability to be obtained as a uniform polymer with controllable topology and nonequilibrium behavior. Currently, a major obstacle in the widespread adoption of DNA is obtaining it on a scale and cost basis that accommodates bulk rheology and high-throughput screening. To address this, recent advancements in bioreactor-based plasmid DNA production is coupled with anion exchange chromatography producing a unified approach to generating gram-scale quantities of monodisperse DNA. With this method, 1.1 grams of DNA is obtained per batch to generate solutions with concentrations up to 116 mg mL-1. This solution of uniform supercoiled and relaxed circular plasmid DNA, is roughly 69 times greater than the overlap concentration. The utility of this method is demonstrated by performing bulk rheology measurements at sample volumes up to 1 mL on DNA of different lengths, topologies, and concentrations. The measured elastic moduli are orders of magnitude larger than those previously reported for DNA and allowed for the construction of a time-concentration superposition curve that spans 12 decades of frequency. Ultimately, these results can provide important insights into the dynamics of ring polymers and the nature of highly condensed DNA dynamics.

Separation Properties of Plasmid DNA Using a Two-Stage Particle Adsorption-Microfiltration Process

Plasmid DNA is used as a vector for gene therapy and DNA vaccination; therefore, the establishment of a mass production method is required. Membrane filtration is widely employed as a separation method suitable for the mass production of plasmid DNA. Furthermore, the separation of plasmid DNA using microfiltration and ultrafiltration membranes is being investigated. Because plasmid DNA has a circular structure, it undergoes significant deformation during filtration and easily permeates the membrane, hindering the selection of separation membranes based on molecular weight. In this study, we applied affinity microfiltration to plasmid DNA purification. α-Fe₂O₃ with an isoelectric point of approximately 8 and a particle size of 0.5 μm was selected as the ligand for two-stage affinity microfiltration of plasmid DNA. In the first stage of microfiltration, the experiment was conducted at a pH of 5, and a cake of α-Fe₂O₃ with bound plasmid DNA was obtained. Next, liquid permeation (pH 9 and 10) through the cake was performed to elute the bound plasmid DNA. Plasmid DNA was eluted during the early phase of liquid permeation at pH 10. Furthermore, agarose gel analysis confirmed the usefulness of the two-stage affinity microfiltration method with adsorption and desorption for plasmid DNA purification.

Plasmid pVAX1-NH36 purification by membrane and bead perfusion chromatography

The demand for plasmid DNA (pDNA) has increased in response to the rapid advances in vaccines applications to prevent and treat infectious diseases caused by virus, bacteria or parasites, such as Leishmania species. The immunization protocols require large amounts of supercoiled plasmid DNA (sc-pDNA) challenging the development of efficient and profitable processes for capturing and purified pDNA molecules from large volumes of lysates. A typical bioprocess involves four steps: fermentation, primary recovery, intermediate recovery and final purification. Ion-exchange chromatography is one of the key operations in the purification schemes of pDNA owing the chemical structure of these macromolecules. The goal of this research was to compare the performance of the final purification step of pDNA using ion-exchange chromatography on columns packed with Mustang Q membranes or perfusive beads POROS 50 HQ. The experimental results showed that both matrixes could separate the plasmid pVAX1-NH36 (3936 bp) from impurities in clarified Escherichia coli lysates with an adequate resolution. In addition, a 24- and 21-fold global purification factor was obtained. An 88 and 63% plasmid recuperation was achieved with ion-exchange membranes and perfusion beads, respectively. A better understanding of perfusion-based matrices for the purification of pDNA was developed in this research.