Generation of lactose and protease positive probiotic Lacticaseibacillus rhamnosus GG by conjugation with Lactococcus lactis NCDO 712.

In this study, we made L. rhamnosus GG lactose and protease positive by conjugation with the dairy Lactococcus lactis strain NCDO 712 carrying the lactose-protease plasmid pLP712. A lactose hydrolyzing transconjugant colony was obtained on agar containing lactose as the sole source of carbohydrates. By microscopic analysis and PCR with LGG- and pLP712-specific primers, the transconjugant was confirmed to be originated from LGG, and to carry the plasmid pLP712. The transconjugant was named L. rhamnosus LAB49. Isolation of plasmids revealed that not only pLP712, but also other plasmids had been transferred from L. lactis into LGG during conjugation. With plasmid-specific PCR primers, four additional lactococcal plasmids were detected in LAB49. Proteolytic activity assay and SDS-PAGE analysis verified that L. rhamnosus LAB49 effectively degraded β-casein. In contrast to its parental strain LGG, the ability of LAB49 to metabolize lactose and degrade casein enabled strong and fast growth in milk. As strains with new properties made by conjugation are not regarded as GMOs, L. rhamnosus LAB49 could be beneficial in dairy fermentations as a probiotic starter culture.Importance Probiotic strain Lacticaseibacillus rhamnosus GG (LGG) is widely sold on market as a probiotic or added as supplement in dairy foods because of its benefits in human health. However, due to the deficiency of lactose and casein utilization, LGG does not grow well in milk. On the other hand, lactose intolerance ...
Source: Applied and Environmental Microbiology - Category: Microbiology Authors: Tags: Appl Environ Microbiol Source Type: research