DNA isolation of protozoa - (Dec/07/2005 )

protozoans are predators of bacteria...so when we take culture pellet for DNA isolation it also has bacterial mass and the food like starch etc. (as i usually add wheat grains) in it...the DNA (genomic) obtained after phenol chloroform extraction and absolute alcohol precipitation, i think, is not only of protozoa but also of all other organisms present...
is there any method to obtain pure protozoan DNA?
i am working on metallothioniens.

any help in this regard?
thanks in advance