Efficacy of ficin and peroxyacetic acid against Salmonella enterica serovar Thompson biofilm on plastic, eggshell, and chicken skin.

Salmonella is the leading cause of zoonotic foodborne illnesses worldwide and a prevalent threat to the poultry industry. For controlling contamination, the use of chemical sanitizers in combination with biological compounds (e.g., enzymes) offers a solution to reduce the chemical residues. The current study investigated the biofilm reduction effects of a food-grade enzyme-ficin-and a common sanitizer-peroxyacetic acid (PAA)-against an emerging pathogen, Salmonella enterica ser. Thompson, on plastic, eggshell, and chicken skin surfaces. Results showed that PAA could kill S. Thompson, but ficin cannot. Maximum biofilm reduction was 3.7 log CFU/cm2 from plastic after individual treatment with PAA. However, sequential treatment of ficin and PAA led to biofilm reductions of 3.2, 5.0, and 6.5 log CFU/cm2 from chicken skin, eggshell, and plastic, respectively. Fourier-transform infrared spectroscopy and microscopic analysis confirmed that ficin increased PAA action, causing biofilm matrix destruction. Moreover, the quality of the food surfaces was only altered by 12.5 U/mL ficin and was not altered by PAA. This combined use of enzyme and sanitizer solved major safety issues and proved promising against S. Thompson-associated contaminations in poultry and poultry processing lines.

Inhibitory effects of Flavourzyme on biofilm formation, quorum sensing, and virulence genes of foodborne pathogens Salmonella Typhimurium and Escherichia coli.

Salmonella enterica and Shiga toxin-producing (or verotoxin-producing) Escherichia coli are major foodborne pathogens, posing substantial food safety risks. Due to the negative effects of chemical treatment against foodborne pathogens, the application of enzyme-based techniques is currently receiving great attention. Here, we evaluated the inhibitory properties of Flavourzyme, a commercial peptidase, against these two foodborne pathogens. We noticed 4.0 and 5.5 log inhibition of biofilm formation by S. Typhimurium and E. coli, respectively, while treated with sub-minimum inhibitory concentrations of Flavourzyme for 24 h. For both bacteria, the enzyme exhibited quorum-quenching activity, preventing autoinducer-2 production completely by E. coli. In addition, Flavourzyme significantly suppressed the relative expression levels of biofilm-forming, quorum sensing, and virulence regulatory genes as measured by qRT-PCR. Based on our results, we suggest the use of Flavourzyme as a preventive agent against foodborne pathogens that possibly acts by inhibiting bacterial self-defense mechanisms following disruption of cellular proteins. This finding may shed light on how enzymes can be applied as a novel weapon to control foodborne illnesses to ensure food safety and public health.