Efficacy of Organic Peroxyacids for Eliminating Biofilm Preformed by Microorganisms Isolated from Dairy Processing Plants.

The aim of this study was to evaluate the ability of microorganisms isolated from the dairy industry to form biofilms and to investigate the efficacy of organic peroxyacids (peracetic, perpropionic, and perlactic acids and BioDestroy) to eradicate those biofilms. Eighteen microorganisms were isolated from Quebec dairy processing plants that have issues associated with biofilm formation and were presumptively identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry. The single-species biofilm-producing ability of the isolates was then evaluated using 96-well microplates. Eight out of 18 of these isolates were identified as moderate or strong biofilm producers, and 10 out of 18 were negative or weak biofilm producers. The efficacy of the above-mentioned disinfectants was tested on the stronger biofilm-producing bacteria using the MBEC (minimum biofilm eradication concentration) assay. After 5 min, all disinfectants tested successfully eradicated both the single and mixed biofilms when applied following the recommended concentration. However, the efficacy of organic peroxyacids was significantly variable at lower concentrations. For example, 25 ppm of BioDestroy was sufficient to eradicate all the biofilms, except for Pseudomonas azotoformans PFl1A. Unfortunately, microscopic observations highlighted those dead cells were still attached to the surfaces. In conclusion, our results suggest that some microorganisms found in dairy plants can produce tenacious biofilms that are still susceptible to disinfectants, including organic peroxyacids. Further studies would be needed to confirm these observations using a dynamic method to mimic in vivo conditions. IMPORTANCE Biofilm-forming microorganisms are a major issue in the food industry, including the dairy industry, because of their negative impact on product quality. Biofilms are difficult to remove by clean-in-place (CIP) procedures commonly used in processing plants and may be less sensitive to sanitizers. Therefore, it is important to identify these microorganisms to develop biofilm control strategies. The results gathered in the present study could contribute to this aim, even though it was carried out using only static methods.