May i know isolation of antibitic process from bacterial fermented borth or any reference in detail ?

I have fermented broth showing antibacterial activity but not able to purify active compound, what is principle to remove coloured impurities, water soluble or other compound, what is the acidification, precipitation, crystalization. Is any good books on the basic principle of thise work. I am just using ethylacetate and butanol but how to remove coloured impurities and other byproduct, some researchers has used pH drift and other ways but i can not get the basic principle behind it. If any body gives me any reference of book related with this will be gratful to him/her. If i may know the principle then i can use method. why to use methanol or acetone precipitation, what it will do? what pH drift does in broth, what type of molecules can be in fermented broth, how to clarify the broth. may reply to e mail charitrakumarmishra at yahoo.com