Pathogenic biofilms that form on food processing equipment/surfaces are of great concern, because these
can readily lead to food spoilage, bio-fouling, food-borne illness, and their recalcitrance can result in the
acquisition of multi-drug resistance. Currently available coatings do not completely inhibit microbial
growth and an increased demand for such coatings means that new products will need to be developed.
The unique properties of antimicrobial soy isoflavones, including their biodegradability, biocompatibility,
and lack of toxicity as edible products, make their application more appealing than artificial polymer or
chemical-based coatings. In this study, we evaluated the antimicrobial efficacy of soy isoflavones against
pathogenic biofilms of Listeria monocytogenes, Escherichia coli, Pseudomonas aeruginosa, and MethicillinResistant
Staphylococcus aureus (MRSA) using microtiter plate assays (MPAs), scanning electron microscopy
(SEM), and atomic force microscopy (AFM). Ultrasonication technique yielded 491 mg of isoflavones
per gram of soy flour sample. MPA assays and the imaging experiments revealed that the establishment
of L. monocytogenes and E. coli biofilms was inhibited by 10 mg/mL and 100 mg/mL soy isoflavones, while
MRSA and P. aeruginosa were largely unaffected.