After growth in MRS or LAPTg broth, strains were washed 3 times with saline solution (0.85% wt/v NaCl), resuspended in this solution at the original culture volume, and used to inoculate at 4%
(v/v) folic acid casei medium (FACM, Difco, USA) that were then incubated without agitation at 30 C for 18 h.