Green Catanionic Gemini Surfactant-Lichenysin Mixture: Improved Surface, Antimicrobial, and Physiological Properties

Abstract

Catanionic surfactant mixtures form a wide variety of organized assemblies and aggregates with improved physicochemical and biological properties. The green catanionic mixture (NN omega)-N-alpha-Bis(N(alpha)caproylarginine) alpha,omega-propyldiamide (C-3(CA)(2)):Lichenysin (molar ratio 8:2) showed antimicrobial synergies against Yersinia enterocolitica, Bacillus subtilis, Escherichia coli O157:H7, and Candida albicans. Flow cytometry and viability studies indicated that this catanionic mixture increases the probability of Y. enterocolitica (38.2%) and B. subtilis (17.1%) cells entering a viable but nonculturable state. Zeta potential showed that one of the cationic charges of C-3(CA)(2) is neutralized by Lichenysin. An isotherm study demonstrated the formation of a stable aggregate between the two surfactants. The catanionic aggregate was able to interact with bacterial phospholipids. The lowest hemolysis (22.1 mu M) was obtained with the catanionic mixture, although an irritant potential (0.70) was characterized. According to the therapeutic index, the C-3(CA)(2):Lichenysin mixture was the formulation least toxic to eukatyotic cells. Partial neutralization of C-3(CA)(2) by Lichenysin modified the mode of action that enhances the transition of bacterial cells into a viable but nonculturable state (VBNC) and improved the cell selectivity. KEYWORDS:antimicrobial activity catanionic mixtures biosurfactant Lichenysin gemini surfactants flow cytometry VBNC Langmuir balance