RATIONAL SELECTION OF LACTOBACILLUS STRAINS BASED ON BILE SALT HYDROLASE ACTIVITY

Lactobacillus species form an integral part of the human gut microbiome. They are frequently applied as probiotics with the prerequisite that they can metabolize bile acid (BA). Bile salt hydrolase (BSH) enzymes are the gateway reaction for BA metabolism by gut microbes (Jones, Begley et al. 2008). BSH removes a glycine or taurine moiety conjugated to a bile acid yielding free BAs, these can then be subsequently further microbially modified. These modifications can result in alterations in host physiology (Joyce, MacSharry et al. 2014). Within the L.salivarius species alone allelic variation of the BSH proteins have been divided into four major groups, all of which have distinct differences (Fang, Li et al. 2009), one of these has been shown to be a significant factor in the reduction of host weight gain (Joyce, MacSharry et al. 2014). This study applied rational selection and screening to isolate and identify new strains of Lactobacillus with BSH enzymes with specific activities. Six isolates, of either pig or human origin, were characterized genetically and phenotypically, for their ability to alter BAs and for their physiological effect on the murine host. Their potential in conferring health benefits is discussed.