Effect of the antibiotics kanamycin and ampicillin on the growth and phase variation of the populations of four strains of lactic acid bacteria (Lactobacillus sp. M76AT, L. casei MB, Enterococcus faecium M, and E. faecium M3185) was studied. The presence of antibiotics in the medium resulted in a dose-dependent decrease in viable cell numbers and in partial or complete substitution of the dominant S variant with the minor Sm and Sb variants. The variants differed in colony morphology, as well as in some physiological, biochemical, biotechnological, and probiotic characteristics. The Sm type variants of all strains exhibited the highest resistance to antibiotics. High production of exopolysaccharides was found in Sb variants of lactobacilli and in S variants of enterococci. The highest antibacterial activity was found in Sm variants of lactobacilli, especially in Lactobacillus sp. M76AT. The latter is biotechnologically the most promising strain, since all variants fermented milk yielding the products with uniformly pronounced functional and organoleptic properties. These patterns are of importance for the understanding of the mechanisms of antibiotic resistance and for selection of the variants with desired properties, as well as for quality control of the lactic acid bacteria starter cultures.

The surface activity and dynamics of adsorption surface layer formation of individual solutions of 5-methylresorcinol (MR) and its mixed solutions with lysozyme on air/solution (0.05 M phosphate buffer, pH 6.0) interface under conditions of MR maximally exceeding hydrolytic activity of lysozyme are studied using method of dynamic drop tensiometry. The thermodynamic parameters of adsorption are determined based on the isotherms. It is established that MR possesses lower surface activity in comparison to traditional surfactants. Methylresorcinol increases the surface activity and lysozyme adsorption rate at the air/solution interface in the entire concentration range covered.

Методом динамической капельной тензиометрии исследована поверхностная активность и динамика формирования адсорбционных слоев индивидуальных растворов 5-метилрезорцина (МР) и его смешанных растворов с лизоцимом на межфазной границе воздух/раствор (0.05 М фосфатный буфер, pH 6.0) в условиях, когда МР максимально повышает гидролитическую активность лизоцима. На основе изотерм определены термодинамические параметры адсорбции. Установлено, что МР обладает более низкой поверхностной активностью в сравнении с традиционными ПАВ. Метил-резорицин повышает поверхностную активность и скорость адсорбции лизоцима на границе воздух/раствор во всем диапазоне использованных концентраций.