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.