Determination of Bile Salt Hydrolase Activity in Bifidobacteria.

Bile salt hydrolase (BSH) activity is a desirable trait in putative probiotic bacteria, such as those belonging to the Bifidobacterium genus. On the one hand, bile salt hydrolysis is considered to represent a bile detoxification mechanism for gut commensal bacteria and thus the presence of this activity was believed to be a predictor of bile tolerance of putative probiotic strains. On the other hand, it has recently been revealed that chemical modifications of the bile acid pool performed by the gut microbiota strongly impact on host health. This explains the increasing interest to investigate the role played by bile-modifying enzymes of gut commensals on lowering cholesterol levels, on modulating gut inflammation or on influencing the development of cancer or metabolic disorders. This chapter compiles qualitative and quantitative methods to analyse BSH activity in bifidobacteria, though they could be adapted to other bacterial groups of interest.