Microbial surface active substances (SAS, surfactants) due to a complex of physicochemical (ability to emulsify, decrease surface and interfacial tension) and biological (antimicrobial and antiadhesive activity, ability to biofilms destruction) properties are multifunctional preparations, promising for use in various industries and environmental technologies. However, a significant disadvantage of these microbial synthesis products is the dependence of their properties of producers growing conditions, since surfactants are secondary metabolites and synthesized as a complex of similar compounds, the composition and ratio of which can change under different cultivation conditions.
According to the literature, the main approaches to the regulation of biological activity of microbial surfactants are their post-fermentation chemical modification, as well as the improvement of producer strains by methods of metabolic and genetic engineering.
The dissertation is devoted to the development of simpler, but no less effective ways of regulation of antimicrobial and antiadhesive activity of surfactants synthesized by Nocardia vaccinii IMV B-7405.
The dissertation shows that the detection of potential activators and / or inhibitors of key enzymes of the components microbial surfactant complex biosynthesis, responsible for certain properties, followed by appropriate modification of the nutrient medium composition allows to regulate the composition of the complex and, consequently, the properties of target product. Thus, it was found that the key enzyme of biosynthesis of N. vaccinii IMV B-7405 surface-active aminolipids - responsible for antimicrobial activity of surfactants is NADP+ -dependent glutamate dehydrogenase, the activators of which are cations of calcium, sodium and potassium. The increase of IMV B-7405 strain culture medium concentration of calcium chloride from 0.1 to 0.4 g/l or application additional of 0.5-1.0 g/l of sodium chloride, potassium chloride or there mixture was accompanied by an increase in NADP+-dependent glutamate dehydrogenase activity by 1.5-3 times, as well as enhancing the antimicrobial and antiadhesive activity of the synthesized surfactants, the minimum inhibitory concentrations (MIC) of which against to bacterial (Bacillus subtilis BT-2, Escherichia coli IEM-1, Staphylococcus aureus BMS-1) and yeast (Candida tropicalis PE-2, Candida albicans D-6 Candida utilis BVS-65) test cultures were 1.8−125 times lower, and the adhesion of test cultures on abiotic surfaces treated with such surfactants, 1.1−1,6 times lower compared to the established for surfactants obtained on the basis medium without additional introduction of cations.
Key words: Nocardia vaccinii IMV B-7405, surfactants, regulation, antimicrobial and antiadhesive activity.
