Lactobacillus rhamnosus GG Genomic and Phenotypic Stability in an Industrial Production Process

GG is one of the most widely marketed and studied probiotic strains. In GG, the gene cluster encodes pili, which are important for some of the probiotic properties of the strain. A previous study showed that the DNA sequence of the gene cluster was not present in some GG variants isolated from liquid dairy products. To examine the stability of the GG genome in an industrial production process, we sequenced the genome of samples of GG (DSM 33156) collected at specific steps of the industrial production process, including the culture collection stock, intermediate fermentations, and final freeze-dried products. We found that the GG genome sequence was unchanged throughout the production process. Consequently, the gene locus was intact and fully conserved in all 31 samples examined. In addition, different production batches of GG exhibited consistent phenotypes, including the presence of pili in final freeze-dried products, and consistent characteristics in assays of probiotic properties. Our data show that GG is highly stable in this industrial production process. GG is one of the best-studied probiotic strains. One of the well-characterized features of the strain is the pili encoded by the gene cluster. These pili are involved in persistence in the gastrointestinal tract and are important for the probiotic properties of GG. Previous studies demonstrated that the GG genome can be unstable under certain conditions and can lose the gene cluster. Since studies have shown that the loss of the gene cluster decreases certain GG probiotic properties, we assessed both the genomic stability and phenotypic properties of GG throughout an industrial production process. We found that neither genomic nor phenotypic changes occurred in the samples. Therefore, we demonstrate that GG retains the cluster and exhibits excellent genomic and phenotypic stability in the specific industrial process examined here.