Efeito do pH e força iônica na atividade antimicrobiana de ramnolipídeos frente à Staphylococcus aureus

Abstract

Foodborne diseases (FBD) are considered to be one of the most important causes of mortality in developing countries and bacteria one of the main factors causing these pathologies. Among them, diseases caused by Staphylococcus aureus are harmful both by infection of the host organism and intoxication by enterotoxins present in contaminated and poorly stored foods. Bacterial resistance to conventional antibiotics, together with the interest in more sustainable antimicrobials, demands the search for alternative methods of control. In this context, the use of biosurfactants (BS), such as rhamnolipids (RL), is promising since they have low toxicity, are biodegradable and synthesized from renewable sources. The main objective of this study was to evaluate the effect of pH and ionic strength on antimicrobial activity of RL against S. aureus. The results show that increasing pH from 5 to 7 also increased the minimal inhibitory concentration ( MIC) from 78,12 mg/L to > 2500 mg/L. In the same way, increasing the NaCl levels favored the antimicrobial activity of RL in all pH tested. The ionic strength and pH affect significantly in RL activity against S. aureus and can be exploited to inhibit such bacteria in salted and acid foods.