Bile salt hydrolase activity, growth characteristics and surface properties in Lactobacillus acidophilus

Thirteen strains of Lactobacillus acidophilus of various origins were tested for bile salt hydrolase (BSH) activity, growth characteristics and surface properties during cultivation in the presence of ox bile. Seven strains were BSH positive, three strains were found to hydrolyse both sodium glycocholate and taurocholate and four hydrolysed only glycocholate. The addition of ox bile (3; 5 or 10 g/l) to MRS growth medium affected the growth rate of both BSH-positive and BSH-negative strains. The lag phases were increased when 5 or 10 g/l of ox bile were added. Growth rates and lag phases were significantly different between BSH-positive and BSH-negative strains in MRS medium with bile. BSH-positive strains were better able to adapt to increasing bile concentrations. The concentration of 2 g/l sodium cholate completely inhibited growth of all lactobacilli tested. Its toxicity was influenced by pH of medium. The addition of 3 g/l ox bile affected the properties related to ability of lactobacilli to adhere to surfaces––autoaggregation increased in all strains and zeta potential only in BSH-negative strains. In all strains tested, bshA and bshB genes were identified with the exception of L. acidophilus Lafti-L10. Repeated cultivation in MRS with bile did not cause the expression of genes in BSH-negative strains.