Niche adaptation of Lactobacillus delbrueckii: Ecological insights on the role of β-glucosidases in the biotransformation of glycosylated phytochemicals

ABSTRACT Carbohydrate metabolism plays a central role in the competitiveness of Lactobacillus delbrueckii. This study aimed to identify the complement of carbohydrate-active enzymes present in different subspecies of L. delbrueckii and to evaluate the transformation of disaccharides and glycosylated phytochemicals by β-glucosidases. Using comparative genomics, phylogenetic analysis, and analyses of carbohydrate utilization, the "CAZome" of 2 bovine isolates, L. delbrueckii ssp. lactis L10 and L13 from neonatal calves, one piglet strain L. delbrueckii Swine1, and 2 food isolates L. delbrueckii ssp. lactis FUA3175 and L. delbrueckii ssp. bulgaricus FUA3291, were examined. Phylogenetic analysis revealed a distinct clustering of subspecies within the phylogenetic tree. Bovine isolates of L. delbrueckii ssp. lactis clustered with food isolates, whereas L. delbrueckii Swine1 formed a separate cluster with other piglet strains. The genomes of L. delbrueckii ssp. lactis and the swine lineage encoded 4 and 5 (6-phospho)-β-glucosidases, respectively, whereas the L. delbrueckii ssp. bulgaricus genome encoded only for one. Lactobacillus delbrueckii Swine1 but not the other strains of L. delbrueckii converted the glycosylated phytochemicals amygdalin, salicin, daidzin, and genistin. In conclusion, these findings highlight the adaptation of L. delbrueckii ssp. lactis and the swine lineage to suckling animals. Whereas L. delbrueckii ssp. lactis is also found in food fermentations, the swine isolates are restricted to the animal host.