A plasmid DNA extract, suitable for specified / unspecified applications (e.g. transfection), is prepared by alkaline lysis and a series of precipitations only. The method can be performed at scale and uses only standard bulk chemical reagents. Plasmid DNA is obtained by alkaline lysis (which can be performed at scale in a stirred tank reactor or other vessel) followed by 3 precipitations. The first and third precipitation s serve to extract plasmid DNA as well as other nucleic acids. The majority of RNA / protein is removed by the second selective precipitation. The final DNA extract typically contains residual RNA and LPS. RNA may be removed, if desired, by digestion with RNase directly before application. The method has been used so far to extract plasmid DNA at the 50-100mg scale using standard laboratory process equipment. The extraction and recovery of plasmid DNA extract from E.coli can be performed quickly (process time for 50-100mg extraction 2.5 hours). The method can be performed by a semi - skilled technician with little specialist training using standard laboratory / process equipment, it may also be suited to automation for multiple small scale DNA preparations.

Potential Commercial applications

¨ Small, medium, large scale DNA manufacturing.