Anti-listerial activity of thermophilin 110 and pediocin in fermented milk and whey

Authors: CERUSO, MERINA - University Of Naples; Liu, Yanhong; Gunther, Nereus - Jack; PEPE, TIZIANA - University Of Naples; ANASTASIO, ANIELLO - University Of Naples; Qi, Phoebe; Tomasula, Peggy; Renye, John

Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/25/2021
Publication Date: 1/31/2021
Citation: Ceruso, M., Liu, Y., Gunther, N.W., Pepe, T., Anastasio, A., Qi, P.X., Tomasula, M.M., Renye Jr, J.A. 2021. Anti-listerial activity of thermophilin 110 and pediocin in fermented milk and whey. Food Control. https://doi.org/10.1016/j.foodcont.2021.107941.
DOI: https://doi.org/10.1016/j.foodcont.2021.107941

Interpretive Summary: Listeria monocytogenes is a bacterium associated with foodborne illness from consuming ready-to-eat (RTE) foods, including dairy products, due to its ability to grow at refrigeration temperature. Research is needed to prevent listeria contamination of RTE foods while maintaining their clean label status. Lactic acid bacteria, which are commonly used for production of dairy foods (yogurt), have been shown to naturally produce compounds, called bacteriocins, that have the potential to meet both requirements and serve as bio-preservatives. This study demonstrated that Listeria survival was significantly reduced in pasteurized skim milk fermented with two dairy cultures known to produce these bioactive compounds; and that potentially novel compounds, capable of inhibiting Listeria growth, could be generated through fermentation of raw milk with lactic acid bacteria. More studies are required to characterize compounds produced from raw-milk fermentation, but these findings suggest that natural compounds produced through milk fermentation with lactic acid bacteria can prevent Listeria contamination of RTE foods.

Technical Abstract: Listeria monocytogenes is a pathogenic bacterium responsible for foodborne illness worldwide. Antimicrobial peptides, or bacteriocins, naturally produced by food-grade lactic acid bacteria have the potential to serve as natural preservatives to prevent the growth of Listeria in a variety of foods, including dairy products. This study investigated the anti-listerial activities of bacteriocin-producing lactic acid bacteria, Streptococcus thermophilus B59671, and Lactobacillus plantarum 076. In vitro studies showed that the concentration of pediocin naturally produced by L. plantarum 076 (2,560 AU ml-1) inhibited the growth of a six-strain cocktail of L. monocytogenes. However, the concentration of thermophilin 110 produced by S. thermophilus B59671 (320 AU ml-1) only delayed the growth by ~2 h. Higher concentrations of thermophilin 110 (= 640 AU ml-1) suppressed Listeria growth for up to 22 h. Pasteurized skim milk fermented with a co-culture of S. thermophilus B59671 and L. plantarum 076 reduced the number of L. monocytogenes cells by > 4 Log CFU ml-1 due mainly to the activity of pediocin. The anti-listerial activity was not observed in whey samples collected from pasteurized skim milk fermented with this co-culture but was detected when raw milk was the substrate. Two additional whey solutions, the by-products from commercial bovine and goat raw-milk cheeses, also inhibited Listeria growth and reduced the number of cells following storage at 4°C for 1 week. This study demonstrated the prospect of using pediocin-producing cultures to inhibit Listeria growth in dairy foods and that a concentrated preparation of thermophilin 110 has potential as an anti-listerial compound. Additionally, metabolites with novel antimicrobial activities may be generated during the fermentation of raw milk due to indigenous microflora and should be evaluated for their potentials in food safety applications.