Process and equipment for plasmid purification
A scalable alkaline lysis process, including procedures and devices for the isolation of large quantities (grams and kilograms) of plasmid DNA from recombinant E. coli cell. Effective, contgrollable, and economical operation, and consistent low level of host chromosomal DNA in the final plasmid product. Involves a series of new unit operations and devices for cell resuspension, cell lysis, and nuetralization.
1. A method of purifying gram quantities of plasmid DNA from a bacterial cell solution, the method comprising the steps of:
lysing bacterial cells containing plasmid DNA with a lysis solution to form a lysate solution;
removing contaminants from the lysate solution by precipitating the contaminants from a supernatant of the lysate solution; and
recovering plasmid DNA from the supernatant using column chromatography over a tentacle anion exchange resin.
2. The method in claim 1 wherein the tentacle anion exchange resin is a trimethylaminoethyl (TMAE) tentacle resin.
3. The method in claim 2 wherein the use of the TMAE tentacle anion exchange resin comprises the step of eluting the plasmid DNA via a step gradient.
4. The method in claim 1 wherein the tentacle anion exchange resin has a particle size of 20–40 microns.
5. The method in claim 2 wherein the TMAE tentacle anion exchange resin comprises a methacrylate based copolymer having a tentacle linked TMAE functional group.
6. The method in claim 2 wherein the plasmid DNA is eluted from the TMAE tentacle anion exchange resin with a salt solution comprising about 1.9 M ammonium sulfate or at least 0.7M NaCl.
7. The method in claim 1 wherein the step of recovering plasmid DNA from the supernatant comprises the steps of:
passing the supernatant through a tentacle anion exchange resin ; wherein the plasmid DNA binds to the resin;
eluting the plasmid DNA in a first eluate from the resin;
adjusting a salt concentration of the first eluate to contain at least 2M ammonium sulfate;
passing the first eluate through a hydrophobic interaction resin, wherein supercoiled plasmid DNA binds to the hydrophobic interaction resin; and
eluting the supercoiled plasmid in a second eluate from the hydrophobic interaction resin via an eluent having less than 2M ammonium sulfate.
8. A method for removing contaminants from a plasmid DNA solution comprising:
a) contacting a solution comprising plasmid DNA with a tentacle anion exchange resin, the solution having a conductivity at which the plasmid DNA is bound to the resin;
b) washing the resin to elute the contaminates; and
c) eluting the plasmid DNA with a step or continuous gradient of increasing conductivity.
9. The method of claim 8 , wherein the tentacle anion exchange chromatography resin comprises tentacles having about 15 to about 50 units in length.
10. The method of claim 8 , wherein the tentacle anion exchange chromatography resin comprises tentacles having an average of about 18 charged groups covalently bound to each tentacle.
11. The method of claim 8 , wherein the tentacle anion exchange resin is a strong anionic changer resin.
12. The method of claim 8 , wherein the tentacle anion exchange resin has TMAE functional groups.
13. The method of claim 8 , wherein the plasmid DNA solution is a clarified lysate obtained after alkaline lysis of bacterial cells comprising the plasmid DNA and removal of precipitated proteins, chromosomal DNA and cell debris.
14. The method of claim 8 , further comprising a step of hydrophobic interaction chromatography (HIC).