Can potential probiotic bacteria make germ-inhibiting substances in conditions resembling the large intestine?

Details

This in vitro laboratory study evaluated whether three bacteriocin-producing probiotic candidates could grow and produce active bacteriocins in Macfarlane broth, which mimics the nutrient composition of the human large intestine. The strains were Lactococcus lactis subsp. lactis biovar diacetylactis UL719, which produces nisin Z; L. lactis ATCC 11454, which produces nisin A; and Pediococcus acidilactici UL5, which produces pediocin PA-1.

The researchers grew all three strains in both Macfarlane broth and De Man-Rogosa-Sharpe (MRS) broth. For each strain, they measured bacterial counts, the drop in pH, and production of organic acids and bacteriocins at different time points. They also used co-culture experiments in Macfarlane broth to examine whether these probiotic candidates could inhibit Listeria ivanovii HPB 28.

All three strains—Lactococcus lactis subsp. lactis biovar diacetylactis UL719, L. lactis ATCC 11454 and Pediococcus acidilactici UL5—grew and produced their bacteriocins in both MRS and Macfarlane broth. Each candidate inhibited L. ivanovii HPB 28, and this inhibition was correlated with bacteriocin production. For P. acidilactici UL5, an experiment using a pediocin-nonproducing mutant confirmed the role of bacteriocin production in inhibiting L. ivanovii in Macfarlane broth.

The authors concluded that the data provide some evidence that these bacteria can produce bacteriocins in a complex medium with carbon sources similar to those found in the colon. The study demonstrates the capacity of these lactic acid bacteria to produce their bacteriocins in a medium simulating the nutrient composition of the large intestine.