1. A strain of bacteria selected from the group consisting of Lactococcus lactis subsp. lactis LcL13 (FERM BP-11276), Lactococcus lactis subsp. lactis LcL26 (FERM BP-11277) and Lactococcus lactis subsp. cremoris LcC46 (FERM BP-11275) .2. Sourdough fermentation of milk raw materials containing the bacterium Bifidobacterium, which comprises a bacterial strain selected from the group consisting of Lactococcus lactis subsp. lactis LcL13 (FERM BP-11276), Lactococcus lactis subsp. lactis LcL26 (FERM BP-11277) and Lactococcus lactis subsp. cremoris LcC46 (FERM BP-11275) .3. Sourdough fermentation of raw milk containing Bifidobacterium bacteria of Claim 2, wherein the bacterium is Bifidobacterium strain is Bifidobacterium longum ATCC BAA-999.4. A method for producing a fermented food product comprising fermenting raw milk using a strain of bacteria selected from the group consisting of Lactococcus lactis subsp. lactis LcL13 (FERM BP-11276), Lactococcus lactis subsp. lactis LcL26 (FERM BP-11277) and Lactococcus lactis subsp. cremoris LcC46 (FERM BP-11275), and Bifidobacterium.5 bacteria. A method according to claim 4, wherein the lactic acid bacterium selected from the group consisting of Streptococcus thermophilus and Lactobacillus delbrueckii, is additionally used for fermentatsii.6. A method according to claim 4 or 5, wherein the bacterium is Bifidobacterium strain is Bifidobacterium longum ATCC BAA-999.7. The fermented food product produced by the method according to claim 4 or 6.8. A method for producing a fermented food product comprising fermenting raw milk using Lactococcus lactis, a non-integrated into the cell wall protease, and Bifidobacterium.9 bacteria. A method according to claim 8, wherein the Lactococcus lactis is characterized in that when said bacterium is inoculated into a medium containing 1 wt.% Glucose and 10 wt.% Powder skim milk in an amount of 5.0 × × 10-2,0 on 10KOE 1 ml of medium, and cultured at 37 ° C for 4-24 hours, the medium is not koaguliruet
