Cleaning Basal Media in a Large Tank

Q. Could you please recommend a minimum Solujet concentration, temperature and time for use with a CIP system to wash a large mixing tank dedicated to manufacturing DMEM-F12 basal media.

A. Without actually doing a study with your exact sprayballs and flow rates, I cannot give you precise time, temperatures and concentrations.  I can give you some guidelines based on general experience with medical device cleaning validation.

I am confident that you can clean basal media successfully using 0.5% Solujet (5 mL/L) at 50 deg C for 20 minutes of re-circulation in a large tank. Rinsing would follow.  This is of necessity a conservative recommendation as I have not done specific studies in your equipment. In general every 10 deg C you go down in temperature, you need to double the cleaning time.  At ambient temperature of 20 deg C, in theory you get equivalent cleaning at 160 minutes (doubling the time 3 times).  It would not surprise me at all if the cleaning could be achieved in 10 minutes.

 I do not know the size of the tank and thickness of the residue being removed.  I do not know if there has been a water pre-rinse step.  If the film of residue is pretty thin, there has been a water pre-rinse and the tank is not larger than 1,000 gallons, then I would be pretty confident you can clean in 10 minutes at 50 deg C with 0.5% Solujet. 

You can adjust temperatures and times using the double the time for every 10 deg C decrease rule. I suspect the lowest possibly effective concentration you could try with Solujet is 0.25%, 2.5 mL/L. At this concentration you are pushing the edge of the critical micelle concentration of the surfactant.  You also do not have that much free alkalinity at this concentration.  Only very light films could reliably be cleaned with this concentration.  You would have to establish the efficacy of this low concentration of cleaner.  

I have heard of specific cases of using Solujet at concentrations as low as 0.1% for cleaning on very easy to clean residues. I do not consider basal media to be easy to clean, nor is it very difficult.  The standard recommended dilution for Solujet is a 1% dilution, but because basal media is not as difficult to clean as tenacious water insoluble organic compounds, I have recommended a 0.5% concentration. 

Do you have a technical question? Please visit Ask Alconox.