Gene therapy is a promising process for the prevention, treatment and cure of diseases such as cancer, acquired immunodeficiency syndrome (AIDS) and cystic fibrosis. One of the methods used to administer therapeutic genes is the direct injection of naked or lipid-coated plasmid DNA, but this requires considerable amounts of plasmid DNA. There are several problems and bottlenecks associated with the design and operation of large-scale processes for the production of pharmaceutical-grade plasmid DNA for gene therapy.