STRUCTURE-FUNCTION RELATIONSHIP OF ACYL AMINO-ACID SURFACTANTS - SURFACE-ACTIVITY AND ANTIMICROBIAL PROPERTIES

Amino acid surfactants (AAS), having the general structure alpha-amino -(N-acyl)-beta-alkoxypropionate, were synthesized chemically. Surface activity and antimicrobial properties of the AAS were evaluated. Incre ases in acyl chain length (i.e., C-10-C-14) resulted in a linear reduc tion in surface tension (i.e., 43-36 mN . m(-1)), as well as dramatic decreases in critical micelle concentrations (cmc) (i.e., 17.9-0.43 mM ). Strong correlations existed between the cmc of AAS and their minima l inhibitory concentrations (mic) against Escherichia coli, Pseudomona s aeruginosa, Aspergillus niger, and Saccharomyces cerevisiae. Sensiti vity of the microorganisms to the various AAS followed the order Staph ylococcus aureus > A. niger = S. cerevisiae > E. coli > P. aeruginosa. In comparison with methyl p-hydroxybenzoate, AAS (MN14) showed 2-8, 6 4, and 4-8 times the activity against Gram-negative bacteria, Gram-pos itive bacteria, and fungi, respectively. Surface adsorption and/or bif unctional binding to the cell membrane may account for AAS action on m icroorganisms.