The technique of optical-electrochemical microbiological testing as applied to the comparative analysis of the prebiotic and antimicrobial properties of various plant extracts

A biotesting technique is described that provides for periodic (every 2 h) recording of changes in the intensity of elastic light scattering, pH and electrical conductivity of a liquid nutrient medium incubated in the presence and absence of viable test microorganisms and test samples. The results of a comparative analysis using this technique of antibiotic activity against Staphylococcus aureus of different concentrations of whole subcritical extracts obtained using liquefied CO2 from 10 different types of plant raw materials are presented. Studies have shown that among the samples studied by us, the most active prolonged antimicrobial properties were exhibited by extracts from the roots of Chelidonium majus and flowers of Calendula officinalis at their concentration in the test medium (CTE) more than 3 vol.%. And the most active prolonged prebiotic properties were exhibited by extracts from shoots of Viscum album and leaves of Juglans regia at CTE = 0.2 vol.%. In this case, the biological activity of the tested samples with respect to test microorganisms in most cases monotonically decreased with an increase in the interaction time of the mentioned microorganisms and samples. However, the exact nature of these dependencies in most cases can be established only with the help of a significant number of tests. And the latter can be conveniently carried out using the methodology presented in this work, which allows a much more rapid, objective and informative, as well as much less laborious and materialintensive, than when using standard visual microbiological methods, to assess the effect on the dynamics of the vital activity of microorganisms of various tested samples.