Screening of bacteriocin-producing dairy Enterococcus strains using low-cost culture media

Abstract

This study was carried out to select the bacteriocinogenic strains among Enterococcus strains isolated from Ukrainian traditional dairy products using a low-cost media for screening, that containing molasses and steep corn liquor. A total of 475 Enterococcus spp. strains were screened for antagonistic activity against Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, and Listeria monocytogenes indicator strains. The initial screening revealed that 34 Enterococcus strains during growth in low-cost medium containing corn steep liquor, peptone, yeast extract, and sucrose produced metabolites with inhibition activity against at least of the indicator strains used. Enterocin genes entA, entP, and entB were detected in 5 Enterococcus strains by PCR assay. Genes of enterocins A and P were found in E. faecalis 58 and Enterococcus sp. 226 strains, enterocins B and P – in Enterococcus sp. 423, enterocin A – in E. faecalis 888 and E. durans 248 strains. Bacteriocin-like inhibitory substances (BLIS) produced by these Enterococcus strains were thermostable and sensitive to proteolytic enzymes. To our knowledge, this is the first report on the isolation of enterocin-producing wild Enterococcus strains from traditional Ukrainian dairy products using a low-cost media for screening bacteriocinogenic strains. Strains E. faecalis 58, Enterococcus sp. 423, and Enterococcus sp. 226 are promising candidates for practical use as producers of bacteriocins with inhibitory activity against L. monocytogenes using molasses and steep corn liquor as cheap sources of carbon and nitrogen, that can significantly reduce the cost of industrial bacteriocin production. Further studies will be required to determine the dynamic of bacteriocin production, its structure, and mechanisms of antibacterial action.

Anti-Listerial Activity of Bacteriocin-like Inhibitory Substance Produced by Enterococcus lactis LBM BT2 Using Alternative Medium with Sugarcane Molasses

“…Although glucose is considered the main carbon source for all heterotrophic microorganisms due to its favorable molecular size, rapid uptake utilization and cell energy conversion, some bacteria have an enzymatic machinery that allows them to use more complex carbohydrates. Sucrose is a cheaper carbon source than glucose and has already been reported for bacteriocin production by LAB [ 13 , 28 , 29 ]. Since bacteriocins are generally reported as primary metabolites, the increase in cell density would be a good strategy for enhanced bacteriocin production [ 30 ].…”

“…Bacteriocin production by LAB is usually performed in MRS broth, a complex medium that promotes good growth and enhanced bacteriocin synthesis [ 13 , 14 ]. However, this medium is considered not suitable for large-scale production and industrial applications mainly due to its high cost.…”

“…The potential of molasses-based media for bacteriocin production has already been reported by some authors. Gamasheva et al [ 13 ] reported that the use of low-cost media containing molasses and steep corn liquor resulted in the successful production of enterococci bacteriocins with activity against L. monocytogenes . In the same way, Mulyani et al [ 33 ] evaluated an enriched medium containing 30% molasses for the production of an anti-listerial bacteriocin by Pediococcus pentosaceus 2A2 and highlighted the potential of molasses as a low-cost substrate.…”

“…To produce bacteriocins, complex and expensive culture media such as the De Man, Rogosa and Sharpe (MRS) medium are often used [ 13 ]. The need to make production economically competitive and sustainable encouraged the search for alternative culture media since the culture medium can represent up to 30% of the total production cost in commercial fermentations [ 14 ].…”

“…It can also occur both in food and food chain production, leading to many health and economic losses [1]. Additionally, these microorganisms are able to form biofilm structures, which are resistant to disinfectants (e.g., peracetic acid) and can Antibiotics 2024, 13, 210 2 of 20 lead to the persistence of microbial cells and the formation of secondary biofilms on various surfaces [2].…”