Bactericidal activity of rhamnolipids combined with NaCl against Listeria monocytogenes.

Abstract

Foodborne Diseases (FBD) are growing at high rates along with the increased resistance to conventional antimicrobial treatments. In this context, the antimicrobial property of biosurfactants, such as rhamnolipids (RLs) has been studied as a novel alternative to the control of foodborne pathogens. The RLs are stable at high salt concentration, have low toxicity, and are biodegradable which favors their application in the food industry. This work aims to investigate the effect of sodium chloride (NaCl) in the antimicrobial activity of RLs against Listeria monocytogenes. The Minimum Inhibitory and Bactericidal Concentrations (MIC) and (MBC) values of RLs and RLs-NaCl were determined, in addition to performing Critical Micellar Concentration (CMC) measurements. The results showed a reduction in MIC values from 156.25 mg/L to 39.06 mg/L in the medium containing 5% of NaCl, and MBC from > 2500 to 78.12 mg/L. It was also possible to observe that NaCl reduced the CMC values of the biosurfactant from 94.2 mg/L to 16 mg/L, suggesting that micellar aggregation is related to antimicrobial activity. The presence of NaCl increased the antimicrobial activity of RLs and can be exploited as a promising tool for the control of L. monocytogenes.