An engineered intervention to remove and sanitize embedded Salmonella enterica serovar Typhimurium and Pseudomonas fluorescens cells in egg biofilms from three food-contact surfaces

Salmonella spp. and Pseudomonas spp. are two of the main microorganisms of concern in the egg industry. The potential of foodborne outbreaks and egg quality degradation are related to the presence of these bacteria that can easily contaminate eggs and food-contact surfaces by forming strong biofilms. The requirement for effective interventions to remove biofilms and sanitize food-contact surfaces is therefore a current research priority. This research aimed to investigate a bioengineered recombinant glycosyl hydrolase, CAase (0.150 mg/ml) as a pre-treatment on three food-contact surfaces (stainless steel, silicone, and nylon) for egg biofilm removal containing cells of Salmonella Typhimurium or Pseudomonas fluorescens with a further sanitization step using peracetic acid (PAA) at two different concentrations (e.g., 90 – 120 ppm, for Salmonella and 60 – 90 ppm for Pseudomonas ) and contact times (1 and 3 min). Scanning electron microscopy (SEM) was used to assess the biofilm formation, the effect of CAase and the final PAA sanitizing step. Both microorganisms showed mature biofilms after 24 hours (∼7 and ∼ 6 log, respectively) on the three surfaces without significant differences (p > 0.05). The use of CAase alone allowed some cell inactivation (∼ 2 log) for both microorganisms. The two-step treatment of CAase and PAA for both microorganisms reduced PAA contact time and concentration allowing complete sanitization of the three materials. SEM images showed thick biofilms with embedded microbial cells, the “dissolving effect” of CAase on embedded biofilms and the sanitized food-contact surface after the two-step process. These results offer a green alternative for egg processors to sanitize food-contact surfaces with effective interventions against Salmonella and Pseudomonas cells. • Salmonella and Pseudomonas generated strong egg biofilms in three materials • The enzyme CAase was able to inactivate ∼ 2 log of each microorganism (60 min) • Peracetic acid (PAA) alone did not sanitize the surfaces under tested conditions • CAase and PAA removed and sanitized the three food – contact surfaces • Further studies are required to optimize this two-step sanitation process