INFLUENCE OF CULTIVATION CONDITIONS ON ANTIMICROBIAL AND ANTI-ADHESIVE ACTIVITY OF SURFACTANTS OF BACTERIA OF ACINETOBACTER, RHODOCOCCUS AND NOCARDIA GENERA

Abstract

Microbial surfactants are multifunctional products because they cannot only reduce the surface tension at the interface and emulsify various substrates, but also display antimicrobial and anti-adhesion activity (including the ability to destroy biofilms). However, under various conditions of producer’s cultivation the surfactant composition and their properties can vary. One of the approaches to increasing antimicrobial and anti-adhesion activity of the surfactant can be an increase in medium of producer cultivation content of activators of key enzymes biosynthesis of aminolipids − the most effective antimicrobial agents. Activators of NADP+-dependent glutamate dehydrogenase in Acinetobacter calcoaceticus IMV B-7241 are cations of calcium, magnesium and zinc, Rhodococcus erythropolis IMV Ac-5017 and Nocardia vaccinii IMV B-7405 – calcium.Surfactants were extracted from supernatant of cultural liquid by mixture of chloroform and methanol (2:1). Antimicrobial activity of surfactants was determined by index of minimum inhibitory concentration (MIC), antiadhesive − by spectrophotometry. The degree of biofilm destruction was determined as difference between the number of adhered cells in untreated and treated with surfactant holes of polystyrene immunological plate containing pre-formed biofilm of test cultures and was expressed as a percentage. It was found that addition of CaCl2 (0.1 g/l) into medium cultivation of R. erythropolis IMV Ac-5017, increasing concentration of this salt to 0.4 g/l in medium for N. vaccinii IMV B-7405 growth, introduction of CaCl2(0.1 g l) and increasing MgSO4·7H2O content to 0.2 g/l, or adding Zn2+(38 μM) into medium cultivation of A. calcoaceticus IMV B-7241 was accompanied by synthesis of surfactants MICs of which against test cultures were 1.2–13 times lower, their adhesion on abiotic surfaces treated with such surfactants was on average 10−40 % lower, and the degree of biofilms destruction was 7−20 % higher than indicators established for surfactants obtained on the base medium. The obtained data indicate the possibility of regulating antimicrobial and anti-adhesion activity of microbial surfactants under producer cultivation.