Effect of divalent metal cations on production of gassericin T by Lactobacillus gasseri SBT2055

Abstract

 Gassericin T, a class IIb bacteriocin with two complementary peptides, is produced by Lactobacillus gasseri commonly found in human intestines. L. gasseri strains containing bacteriocinogenic LA158 isolated from a human infant in our laboratory grew well in modified milk-based media, but the gassericin T production by LA158 was inhibited by high concentrations of divalent metal cations in the milk-based media. In this study, it was confirmed that gassericin T production by L. gasseri SBT2055, which has an antiobesity effect, was specifically inhibited in MRS broth by adding divalent metal cations (Mg²⁺, Ca²⁺, Mn²⁺, Fe²⁺, and Zn²⁺) depending on the concentration of cations, although the effective concentrations were different from those in LA158 tested (Mg²⁺ and Ca²⁺). The addition of 200 mM divalent metal cations resulted in the almost complete disappearance of gassericin T despite a good cell growth. Furthermore, gassericin T production was restored by adding trisodium citrate dihydrate (TSC), which is a food-grade chelator of divalent cations. These findings may contribute to the effective use of bacteriocinogenic L. gasseri strains as probiotics for yogurt manufacture without the inhibition of growth of starter strain(s).