How to remove biofilm

How to remove biofilm

Q. How do you remove biofilms?.

A. The “classic” way to remove biofilms of thermophilic bacilli on stainless steel is to use a two-step process entailing an alkaline cleaner, such as our Solujet™ Low-Foaming Phosphate-Free Liquid brand, followed by an acidic cleaner, such as Citrajet® Low-Foam Liquid Acid Cleaner/Rinse . In our experience we get the best results when the first 3% Solujet (alkaline cleaner) at 75 deg C is applied for 30 minutes and is followed by a cursory rinse. The second step of 3% Citrajet (acidic cleaner) at 75 deg C applied for 30 minutes is followed with a final thorough rinse with water. This two-step process produces a very clean result on stainless steel. For PVC, probably you cannot use 75 deg C temperatures.

If you are not able to achieve the desired 75 deg C temperature for their cleaning cycle, then it is theoretically possible to compensate for reduced temperature by using longer cleaning times. Since the surfactant accelerated alkaline hydrolysis reactions follow first order reaction kinetics, every 10 deg C decrease in temperature a corresponds to a double the reaction time to get the same amount of reaction. So this means in theory if you go down to 35 deg C (circa 90 deg F), you would have to clean for 480 minutes instead of 30 minutes at 75 deg C (doubling the time 4 times for a 40 deg C temperature reduction). In practice I think you would find that the surfactant acceleration mechanism does not quite follow first order reaction kinetics and is in fact more effective at lower temperatures, so you could probably achieve comparable results at less than 480 minutes. In summary, if you cannot get their temperatures above 35 deg C, then one way to clean their tanks and centrifuges would be to clean with 3% Solujet at 35 deg C for 480 minutes (or somewhat less), rinse, then clean with 3% Citrajet at 35 deg C for 480 minutes (or somewhat less) and then rinse thoroughly. Of course this long a cleaning regimen may not be practical in a manufacturing environment. Whatever can reasonably be achieved with regard to raising temperature will shorten the cleaning times.

Additionally, you may want to consider trying an enzymatic cleaner like our product Tergazyme™ Enzyme-Active Powdered Detergent  that contains both protease and surfactants. The protease addresses both the cells and any proteins bound up in the polysaccharide biofilm, whereas the surfactants improve wetting and penetration thru the hydrophobic polysaccharide biofilm. This is advantageous because efficiently removing the biofilm it will lengthen the amount of time until it returns. We recommend that Tergazyme be used as a maintenance step between alkaline/acidic cleaning described above. This intermittent use of Tergazyme as a maintenance procedure will completely remove all dead cells and traces of polysaccharide biofilm which in turn slows down the formation of biofilm and allows the regular cleaning cycle to clean effectively for more cycles. Also, important to note that Tergazyme is a powder that you typically mix 1-3% in cool to warm water (35 deg C would be fine, do not exceed 50 deg C – to ensure integrity and activity of the enzyme). Tergazyme is a high foaming cleaner and would not be suitable for a spray-in-air clean-in-place system. You can pump and gently agitate Tergazyme solutions; however you cannot employ high agitation at an air/solution interface without getting excessive foam. If you have an old biofilm, you might want to do a 30 minute 1-3% Tergazyme clean at 35 deg C before the classic 3% Solujet/3% Citrajet clean above.

We would be happy to supply samples of Solujet, Citrajet and/or Tergazyme on request at Get Sample. Certainly we believe that incorporating an alkaline cleaner and or an enzymatic cleaner will improve the results as compared with some that try just bleach. In our experience, bleach alone when used at concentrations that are suitable for food contact surface does have some efficacy on thermophilic bacilli biofilms, but the efficacy is not persistent. Possibly this is because the bleaching mechanism breaks down membranes at the sulfhydryl groups and unsaturated side chains, you usually eventually experience failure as the exposed labile sites to attack are used up and the biofilm persists underneath. Some people also like to minimize the use of bleach to minimize chloride stress cracking on stainless steel.

Please click here for SDS and technical bulletins of Solujet, Citrajet and Tergazyme.

These cleaners are available from leading suppliers such as VWR, USA Bluebook, Spectrum Chemical etc, or on the Alconox website.