Is this a bacterial Contamination? - White precipitate on surface of medium (Jun/28/2005 )

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I'm running a small size reactor to grow cells. I circulate the medium for 24 hours. After 24 hours or less a white precipitate forms on the bottom of the medium flask. When it occurs, the medium sometimes look turbid and sometimes it is clear. When observed under a microscope, I see a lot of debris (small black dots, some bright fish shape, some long strands..) The particles doesn't look motile. I can't figure out what this is. I sterilize my equipments by soaking with 70% IPA and this white precip is always present.

why don't you try to grow on a agar or broth to see wether is aleve organisms or just a precipitation from your medium?