How to concentrate my protein? - (Feb/21/2010 )

I am new in protein work. I am purifying scretory protein in the growth medium. However, it is too diluted after quantification. What is the easiest way to concnetrate the protein (say if I want to use 100ml broth?)? Many Thanks!

It depends on what materials and equipment do you have in your lab.
- ultrafiltration
- freeze-drying (lyophilization)
- precipitation (acetone, ethanol, methanol, ammonium sulfate)