Developing strategies to increase plasmid DNA production in Escherichia coli DH5α using batch culture

Plasmid DNA (pDNA) production has recently increased as a result of advances in DNA vaccines. The practical development of pDNA vaccines requires high yield and productivity of supercoiled plasmid DNA (sc-pDNA). The yield and productivity are influenced by the host strain, the plasmid, the production process, and especially by growth conditions, such as the culture type and medium. We evaluated different strategies to increase pDNA production by Escherichia coli DH5α in batch culture. The strategies were driven by the development of a four single-factor experimental design and were based on the change of culture media composition in terms of carbon and nitrogen and the modification of the pH control by using NaOH or NH4OH. The results revealed the carbon (50 g/L of glycerol) and nitrogen (8.34 g/L of YESP) concentration in the culture medium and starting pH control with NH4OH when most of the organic nitrogen was consumed. Under these conditions, we obtained a volumetric yield of 213 mg pDNA/L, a specific yield of 10 mg pDNA/g DCW (dry cell weight), 92% of sc-pDNA and a productivity of 17.6 mg pDNA/(L h). The pDNA productivities reached were 42% higher than the productivities reported by other authors applying similar conditions.