The present invention generally relates to the field of probiotic bacteria. In particular, the present invention relates to natural derivatives of the Lactobacillus johnsonii strain CNCM I-1225 with improved properties. For example, the present invention relates to a natural derivative of the Lactobacillus johnsonii strain CNCM I-1225 that is deficient in D-lactic acid production and exhibits an improved viability during product storage.