The increasing volume of consumption of probiotics and functional food products requires determination of standardized criteria for cultures and their exometabolites used in functional products manufacturing. The study was aimed at developing criteria for the estimation and standardization of exometabolites and the colony-forming ability of probiotic strains for functional food production. The work included such microbiological and physicochemical methods as GC-MS, GPC, UV, and FT-IR-spectroscopy. Based on the results of the study, the comparative analysis of the microbiological properties of probiotic Bifidobacterium strains was provided, the fatty acid composition of the cell wall was described, and the physical and chemical study of the exopolymers produced by them was carried out. According to the data of FT-IR- spectroscopy, the characteristic features of the components of the cell wall of Bifidobacterium strains were established. Bifidobacteria form the unique composition of organophosphorus structures of lipoteichoic acids, which determines the adhesive ability of strains. The authors studied the molecular weight distribution of the samples of exometabolites isolated from the nutrient medium after the cultivation of bifidobacteria, under conditions of gel-permeation chromatography. The spectral (UV, FT-IR) characteristics of the produced metabolites and their chromatographic fractions were compared. The fatty acids of the Bifidobacterium cell membrane were analyzed using the GC/MS method. The fatty acids were extracted from bacterial cells with different hydrophobicity with a mixture of chloroform and hexane. It has been established that the hydrophobicity is determined by different contents of unsaturated and branched fatty acids in the bacterial membrane. Hydrophobic bifidobacteria are the only that contain the isopentadecane (isoC15:0) and methyl-tetradecanoic (13Me-C14:0) acids. With the mean hydrophobicity, a high content of the isopalmitic (isoC16:0) and stearic (C18:0) acids was established. Low-hydrophobic strains are characterized by a low content of monounsaturated fatty acids.

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