Phage prep DNA yield question

[Robert Roxby]

I'd like to know what kinds of yields people get from lambda phage
preps.  The theoretical maximum from a liter having a titer of
2x10e10 is a mg.  (Never mind that it is hard to get over 1x10e10).
I have pretty good luck concentrating the phage with PEG, getting
almost quantitative recovery.  However, after step and
equilibrium CsCl gradients and formamide extraction of the DNA, I
end up with about 20% of the theoretical amount, 400 ng/liter.
People who have purified enzymes will not quibble over a 20% yield
to purity, but there must be a better way.  You can buy 10 mg of
lambda DNA for $60.  I'm not sure this would cover the price of
25 liters of medium.

Thanks for any insight.
Bob

Biochemistry, Micro- &          rr at bmmb01.umesci.maine.edu
  Molecular Biology             rroxby at maine.maine.edu
University of Maine