Physiological and nutritional studies of Escherichia coli and a new combination of separation methods to obtain highly pure and homogeneous plasmid DNA for gene therapy

A scalable high-cell-density Escherichia coli culture method was established to obtain pharmaceutical grade plasmid DNA (pDNA), together with an optimized purification process. The effects of several components of the medium, such as carbon and nitrogen sources that ensure bacterial nutritional needs, were studied. The operation parameters, such as temperature, shaking and aeration, were set and the optimum values of cell growth and specific pDNA productivity in culture were determined. The subsequent purification process for pharmaceutical grade pDNA was implemented, by combining RNA precipitation with ammonium sulfate and two successive chromatographic steps consisting of size exclusion chromatography and reverse phase-high performance liquid chromatography. This work comprised the first report on the use of reverse phase to purify DNA for application in humans.