RESUMO
Aim: To study the antimicrobial properties of the surface-active agents (surfactants) Acinetobacter calcoaceticus IMV B-7241 depending on the availability of yeast autolysate and trace elements in the composition of ethanol-, n-hexadecane- and glycerol-containing media. Methods: Antimicrobial against bacteria (Escherichia coli IEM-1, Bacillus subtilis BT-2), and yeast (Candida albicans D-6) properties of the surfactant was determined by index of the minimum inhibitory concentration (MIC). Surfactants were extracted from supernatant of cultural liquid by mixture of chloroform and methanol (2:1). Results: The removal from cultivation medium yeast autolysate and trace element mix and replacing them by copper sulfate and iron sulphate in the medium with ethanol and n-hexadecane, and in the medium with glycerol - by potassium chloride, zinc sulfate and copper sulfate accompanied by decreasing antimicrobial properties of surfactants. The most effective antimicrobial agents were surfactant synthesized on ethanol in the presence of yeast autolysate and trace elements (MIC 9-20 µ/ml), whereas the surfactant obtained under similar cultivation conditions on glycerol and n-hexadecane, inhibited growth of tested bacteria and yeast at higher (9-68 and 27-54 µ/ml, respectively) concentrations. The minimum inhibitory concentration of surfactant, synthesized in a medium with ethanol (glycerol, n-hexadecane), yeast autolysate and trace elements, correlated with the activity of NADP+-dependent glutamate dehydrogenase - a key enzyme of aminolipids biosynthesis (610 ± 30, 395 ± 24, 397 ± 24 nM min-1·mg-1 protein, respectively). Conclusions: The higher activity of NADP+-dependent glutamate dehydrogenase when growing the strain IMV B-7241 in a medium with ethanol (n-hexadecane), yeast autolysates and trace elements compared to that in a medium with copper sulfate and iron sulfate, as well as an increase enzyme activity in the presence of zinc cations suggests the possibility of increasing synthesis aminolipids by introducing Zn2+ in the medium with ethanol and n-hexadecan. The obtained data indicate the need for studies depending on biological properties of surfactants of the cultivation conditions of producer.