Exploration of the inhibitory and eradicative effects of diacetyl on Listeria monocytogenes biofilms and its potential application on cantaloupe preservation

Listeria monocytogenes ( L. monocytogenes ) biofilm adhered to food or food contacting surfaces causes food cross-contamination and poses a threat to food safety. Diacetyl, a natural compound produced by lactic acid bacteria, showed efficient anti- L. monocytogenes activity, while its anti-biofilm effects have not been explored yet. Herein, the inhibitory and eradicative effects of diacetyl on L. monocytogenes biofilm were determined, and its potential application on cantaloupe preservation was also assessed. Results showed the minimum biofilm inhibitory and eradication concentration of diacetyl against L. monocytogenes biofilm was 2 and 4 mg/mL, respectively. It was observed that diacetyl could effectively inhibit the biofilm formation through decreasing bacterial metabolism, hydrophobicity, initial bacterial auto-aggregation, as well as cell swimming and swarming ability. Moreover, diacetyl could also down-regulate the expression of the genes relevant to biofilm formation, such as agr A , agr C , sigB, and prfA . Besides, the existing mature L. monocytogenes biofilm could be completely eradicated by diacetyl through disrupting biofilm structural integrity and destroying the extracellular polymeric substances including protein, polysaccharides, and extracellular DNA. Furthermore, diacetyl treatment could eradicate L. monocytogenes biofilm on cantaloupe peels, which achieved a 3.08 Log CFU/cm 2 reduction in bacterial colonization while maintained acceptable color stability, delayed the chlorophyll degradation, and thereby extending the shelf life. These findings demonstrated the dual-functionality of diacetyl against L. monocytogenes biofilms, and suggested its promising application to control and prevent L. monocytogenes biofilms contamination on fresh food produce.