I am trying to adapt CHO K1 cell line to suspension mode. I am following a protocol based on the article here - http://link.springer.com/article/10.1385/MB:15:3:249

I seeded at 100000 cells per mL in a spinner flask. I incubate them at 37 degrees, 150 RPM (recommended is about 80-100) and 5% CO2. I monitor the growth kinetics everyday. Every 3-4 days, when the cells reach a density of 1 million cells per mL, I dilute them to 300000 cells per mL (often I remove some cells and supply fresh media). I use IMDM media with 10% FBS

The cells form clump/aggregate. Is there a solution to this? Can I use an anti-clumping reagent? 

Also, I have no clear idea on when to define that the cells are now adapted to suspension (what i read is that 3 or 4 passages by this process will adapt them). Can someone comment on that?

Thanks.