Modelling Pseudomonas fluorescens and Pseudomonas aeruginosa biofilm formation on stainless steel surfaces and controlling through sanitisers

Pseudomonas spp. contamination was screened from a Minas Frescal cheese processing plant. Biofilm formation of Pseudomonas fluorescens and Pseudomonas aeruginosa and the effect of three sanitisers, peracetic acid, sodium hypochlorite, and chlorhexidine gluconate, on the biofilm production was also studied. The biofilms were formed in milk according to a central composite rotatable design (CCRD) at 0, 1.2, 4, 6.8, and 8 days and 7, 13, 27, 41, and 47 °C. Pseudomonas spp. counts were observed in milking machine, tank, wall, door handle, floor, drain, and cheese. All Pseudomonas spp. isolates showed lipolytic activity and some proteolytic activity. P. fluorescens was able to form biofilms at 9.8–47 °C and 0.9–8 days, while P. aeruginosa formed biofilms at 11–47 °C and 0.7–8 days. Complete biofilm removal was not observed for all sanitisers studied, showing difficulty in sanitising the surfaces after the biofilm formation.