Method for culturing lactic acid bacterium and method for producing fermented milk

A method for producing fermented milk, comprising the steps of:

• a. producing a yogurt mix from raw milk;
• b. providing a concentrated cell suspension containing a bacteriocin producer, which is a bacteriocin-producing lactic acid bacteria belonging to Lactobacillus gasseri, in a concentrated form, by culturing including the steps of, in the order recited:
• (i) adding a proteolytic enzyme to an aqueous whey solution containing whey and water to thereby prepare a culture solution containing whey degraded by the proteolytic enzyme;
• (ii) inoculating said culture solution with Lactobacillus gasseri, said bacteriocin-producing lactic acid bacteria which is said bacteriocin producer;
• (iii) maintaining said culture solution inoculated with said bacteriocin producers at a pH of not lower than 5.2 and not higher than 5.8;
• and
• (iv) separating said bacteriocin producers from said culture solution to provide said concentrated cell suspension;
• c. adding said concentrated cell suspension to said yogurt mix in an amount of not less than 0.01% and not more than 0.1% by weight, based on total weight of said yogurt mix;
• and
• d. fermenting said yogurt mix to which said concentrated cell suspension is added to provide said fermented milk.