The Efficiency of the Preservation of Human Gut Microbiota in Liquid Nitrogen Depending on the Composition of the Cryoprotective Medium

A comparative analysis of the survival rate of the human gut microbiota after low-temperature preservation under the protection of penetrating (dimethylsulfoxide and glycerol), nonpenetrating (gelatin) and gas (helium) protectors was performed. Increased resistance of intestinal bacteria to the effect of low temperatures was revealed. A significant portion of the bacteria (50.0 ± 3.0%) remained viable after freezing in liquid nitrogen without the cryoprotector(s). The greatest survival was achieved under the protection of 5% dimethylsulfoxide (86.0 ± 4.0%), 5% glycerol (82.0 ± 5.2%), and 10% gelatin (75.0 ± 5.0%). The combination of cell-penetrating (dimethylsulfoxide and glycerol) and nonpenetrating (gelatin) protectors did not lead to a synergistic effect. The use of atmospheric helium for cryoprotection of heterogeneous human gut microbiota did not increase its survival, even in combination with such powerful protectors as dimethylsulfoxide and glycerol, which indicates the need to optimize cryoprotection media, in particular, for strict anaerobes.