Method of producing lactic acid bacteria dual-coated with protein and polysaccharide by using protein hydrolysate
The present disclosure relates to a method of producing lactic acid bacteria dual-coated with protein and polysaccharide by using a protein hydrolysate, and lactic acid bacteria having a dual coating, produced by the method. The lactic acid bacteria having a dual coating of protein and polysaccharide, produced according to the present disclosure, have very excellent dry-freezing viability, acid resistance and bile resistance. Accordingly, the lactic acid bacteria having a dual coating of protein and polysaccharide according to the present disclosure will be very useful for the production of fermented milk, processed milk, fermented soy products, processed foods, functional beverages, functional foods, common foods, etc.
1. A method of producing lactic acid bacteria having a dual coating of protein and polysaccharide coatings, the method comprising the steps of:
(a) treating an aqueous protein solution with a protease, thereby preparing an aqueous protein hydrolysate solution;
(b) adding a sugar component and a nitrogen source component for lactic acid bacteria culture to the prepared aqueous protein hydrolysate solution, followed by sterilization, and then inoculating and culturing the lactic acid bacteria in the sterilized aqueous solution;
(c) recovering lactic acid bacteria cells from a fermented lactic acid bacteria culture obtained by the culturing;
(d) adding an aqueous cryoprotectant solution and an aqueous polysaccharide solution to the recovered lactic acid bacteria cells, followed by mixing and homogenization; and
(e) freeze-drying the homogenized aqueous lactic acid bacteria cell solution, wherein the hydrolysis rate of the protein in step (a) is:
(i) a percentage value (%) obtained by dividing a DOD value, which is a difference between the optical density (OD) value (“start-point OD”) of the aqueous protein solution, measured before treatment with the protease, and the optical density (OD) value (“endpoint OD”) of the aqueous protein solution, measured after treatment with the protease, by the start-point OD value; or
(ii) a percentage value (%) obtained by dividing a Δppt value, which is a difference between the measured weight value (“start-point ppt”) of a precipitate, obtained by centrifuging the aqueous protein solution before treatment with the protease, and the measured weight value (“endpoint ppt”) of a precipitate, obtained by centrifuging the aqueous protein solution after treatment with the protease, by the start-point ppt value,
wherein the protein in step (a) is isolated soy protein (ISP),
wherein the concentration of the ISP is 0.45% and the concentration of the protease is 0.015%,
wherein the hydrolysis rate of the isolated soy protein is 74.0%,
wherein the lactic acid bacteria is Bifidobacterium breve CBT BR3 (KCTC 12201 BP).
2. The method of claim 1 , wherein the sugar component for lactic acid bacteria culture in step (b) is one or more selected from the group consisting of fructose, sucrose and glucose.
3. The method of claim 1 , wherein the nitrogen source component for lactic acid bacteria culture in step (b) is yeast extract or soy peptone.
4. The method of claim 1 , wherein the cryoprotectant in step (d) is one or a mixture of two or more selected from the group consisting of trehalose, maltodextrin, mannitol, and skim milk powder.
5. The method of claim 1 , wherein the polysaccharide in step (d) is one or more selected from the group consisting of gums, water-soluble dietary fiber, indigestible maltodextrin, insoluble dietary fiber, starch, Levan, and resistant starch.