Genetic and phenotypic stability of L. paracasei DG
The commercialization of a probiotic microorganism assumes genetic and phenotypic consistency across production lots. However, the large-scale industrial production of probiotic microbial biomasses over years poses a risk of genetic drift, potentially affecting the probiotic's ability to confer health benefits. This study assessed the stability of Lacticaseibacillus paracasei DG (DSM 34154), a commercial probiotic. Seven isolates from different commercial lots over 10 years, one 8-year-old laboratory subculture, one isolate from human feces, and the DG strain deposited at DSMZ were analyzed. Shotgun and PacBio sequencing were combined to obtain the complete genome of the ten isolates. Comparative analysis showed that the seven commercial isolates had identical genomes, differing from the DSMZ isolate by one conservative nucleotide transition and substitution. The laboratory strain had two additional mutations. Phenotypic analyses, including antibiotic resistance, carbohydrate fermentation profile, survival to simulated gastrointestinal transit, immunomodulatory capacity, and radical scavenging ability, found no significant differences among isolates. Overall, this study demonstrates the substantial equivalence of L. paracasei DG during ten years of industrial production, indicating that the current industrial practices may prevent genome alterations that could compromise probiotic performance. Similar studies should be part of continuous monitoring and quality control measures for the probiotic products on the market.