Co‐cultivation of a bacteriocin‐producing mixed culture of Bifidobacterium thermophilum RBL67 and Pediococcus acidilactici UVA1 isolated from baby faeces

Aims:  We investigated the kinetics of growth, metabolism and antimicrobial activity of Bifidobacterium thermophilum RBL67 and Pediococcus acidilactici UVA1 previously isolated as a consortium from human baby faeces and producing antimicrobial proteinaceous compounds. Methods and Results:  Cell growth, antimicrobial activity, glucose consumption, organic acid production and pediocin-gene expression were monitored during pure and mixed strain batch cultures with controlled pH (6·0) at 37°C. The balance of the two strains in mixed cultures was stable, yielding high cell count of 109 CFU ml−1 after a very short incubation time of 4 h for UVA1 and 7 h for RBL67, and RBL67 was not affected by the high production of pediocin by UVA1 during co-culture (up to 12·8 μg ml−1). Furthermore, a real-time PCR assay was developed and allowed gene-expression analysis of the pediocin-gene pedA. Conclusions:  The co-culture of RBL67 and UVA1 showed high stability, cell yields and bacteriocin production during batch cultures and has potential for use as a probiotic mixture with antibacterial properties. In addition, a gene-expression real-time PCR assay was successfully developed, used for the relative quantification of the pediocin transcript pedA and demonstrated to be a valuable complementary tool to activity assay. Significance and Impact of the Study:  This is the first study reporting of a stable mixed culture of two bacteriocin-producing strains of human origin.