Novel lactobacillus strains

A method for obtaining a mutant lactic acid bacterial strain, optionally a Lactobacillus bacterial strain, optionally capable of reducing post-acidification in a fermented milk product in comparison with a parent Lactobacillus bacterial strain, wherein the method comprises subjecting the parent lactic acid bacterial strain to an adaptive evolution, said adaptive evolution comprising a series of evolutionary changes, wherein each next descendent strain of a preceding strain is subjected to a higher environmental temperature than the preceding strain and wherein the mutant lactic acid bacterial strain when present in or added to a fermented milk product is increasing the pH in said fermented milk product in the range of 0.1 to 0.2 during storage of the fermented milk product at about 20° C. as compared to the pH measured under the same conditions in a fermented milk product comprising the parent Lactobacillus bacterial strain, and wherein the pH is determined after storage of said fermented milk product fermented with a starter culture over at least about 14 days at 20° C., and wherein said parent or mutant Lactobacillus bacterial strain is present in a concentration of at least about 107 cell forming units per gram (cfu/g).