Lactobacillus paracasei CICC 20241 produces a 5 kDa bacteriocin, named paracin C, active against
seventeen strains of Alicyclobacillus acidoterrestris used in this study. Paracin C was produced at high
levels in MRS broth at 37 C, reaching a maximum production of 1800 AU/ml using A. acidoterrestris DSM
3922 as target strain. The primary mode of action of paracin C is most probably due to pore formation, as
indicated by the efflux of Kþ from metabolically active cells of A. acidoterrestris. In the presence of 10 mM
gadolinium, paracin C did not affect cells of A. acidoterrestris. This suggests that the mode of action of
paracin C relies on a net negatively charged cell surface. In addition, effect of different medium components
on paracin C production was studied.