Are you sure the problem is lack of biomass? Oftentimes low plasmid yield is due to procedural issues in the plasmid prep and sometimes more cells actually has a lower yield than fewer cells due to inefficient lysis and purification.

Having said that, the limiting factor is often aeration. Use a good medium (Terrific broth or 2YT or something similar) and if you are using flasks you will get much better aeration with baffled flasks shaking at high speed. Be sure the volume used is less than 25% of the flask volume.

The choice of strains can often help as well, a RecA+ strain will grow notably better and denser than a RecA- strain (which most molecular biology strains are).

Hi Michael J. Benedik ,

I will surely keep in mind the aeration aspect!

Thanks,

Subham

Subham Basak , are you trying to separate plasmids from your culture? Your E. coli strain might not be retaining plasmids (plasmid stability).