There are several physical and chemical mechanisms for removing and replacing pathogens from a biofilm on a food contact surface, much more than just producing “inhibitory substances” in a biofilm. In addition to being inhibitory by competing for nutrients or producing some metabolic product that is antimicrobial (i.e., lactic acid), probiotics may act by the following mechanisms:
This mechanism simply populates the food contact surface with probiotic biofilm and prevents the pathogen from making a bond by taking up all the space. Also, the probiotic population may excrete anti-adhesion “molecules” that change the molecular charge or the hydrophobicity of the surface preventing pathogen binding. These probiotic specific molecules will prepare the surface for the new, incoming good bacteria.
2) Biosurfactant Production:
When a probiotic is able to excrete a biosurfactant, this mechanism may break down a biofilm if it already exists. These “slippery detergents” change surface tension allowing the surface to become wet and facilitate dispersion of old biofilm or prevent pathogen adherence by letting them slide away. The Lactobacillus and Bifidobacterium may compete by developing their own niche and biofilm, but first, they will produce a biosurfactant to get rid of any pathogenic biofilm that may be found in a hidden niche on a piece of equipment. These biosurfactants have lower toxicity and higher biodegradability than conventional synthetic surfactants, and they are not easily synthesized by conventional methods.
3) Exopolysaccharide (EPS) Production:
This mechanism involves a matrix released from the cell that dampens down a pathogen’s ability to remain in the processing environment. Also known as anti-adhesion polysaccharides, EPS may modulate the expression of pathogen genes that produce biofilm or surface adhesins. The generated EPS can then eventually aid in the probiotic’s ability to establish its own biofilm.
Click here to see our feature in Food Magazine by Dr. Siobhan O’Reilly