Bacterial growth medium that significantly increases the yield of recombinant plasmid.

Isolation of plasmid DNA from Escherichia coli is a daily activity in many molecular biology laboratories. A number of protocols and media recipes have been reported in an effort to make this process more efficient. Here we describe a growth medium that supports much higher E. coli cell densities and, concomitantly, a much higher yield of plasmid than previously reported for small-scale applications. On a unit volume basis, E. coli cultures grown in this medium, termed H15, produce up to 30-fold more recombinant plasmid than in conventional rich media, paralleling the increase in cell density. This phenomenon is independent of E. coli host strain, DNA insert size and plasmid copy number. H15 medium is also very economical; as much as 6 mg of plasmid can be harvested per dollar of medium.