Growth, acid production and bacteriocin production by probiotic candidates under simulated colonic conditions

Aims The aim of this study is to evaluate the capacity of three bacteriocin producers, namely Lactococcus lactis subsp. lactis biovar diacetylactis UL719 (nisin Z producer), L.lactis ATCC 11454 (nisin A producer) and Pediococcus acidilactici UL5 (pediocin PA-1 producer), and to grow and produce their active bacteriocins in Macfarlane broth, which mimics the nutrient composition encountered in the human large intestine. Methods and Results The three bacteriocin-producing strains were grown in Macfarlane broth and in De ManRogosaSharpe (MRS) broth. For each strain, the bacterial count, pH drop and production of organic acids and bacteriocins were measured for different period of time. The ability of the probiotic candidates to inhibit Listeria ivanovii HPB 28 in co-culture in Macfarlane broth was also examined. Lactococcus lactis subsp. lactis biovar diacetylactis UL719, L.lactis ATCC 11454 and Ped.acidilactici UL5 were able to grow and produce their bacteriocins in MRS broth and in Macfarlane broth. Each of the three candidates inhibited L.ivanovii HPB 28, and this inhibition activity was correlated with bacteriocin production. The role of bacteriocin production in the inhibition of L.ivanovii in Macfarlane broth was confirmed for Ped.acidilactici UL5 using a pediocin nonproducer mutant. Conclusions The data provide some evidence that these bacteria can produce bacteriocins in a complex medium with carbon source similar to those found in the colon. Significance and Impact of the Study This study demonstrates the capacity of lactic acid bacteria to produce their bacteriocins in a medium simulating the nutrient composition of the large intestine.