Submitted to: Journal of Industrial Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 27, 2009
Publication Date: February 1, 2010
Citation: Somkuti, G.A., Steinberg, D.H. 2010. PEDIOCIN PRODUCTION IN MILK BY PEDIOCOCCUS ACIDILACTICI IN CO-CULTURE WITH STREPTOCOCCUS THERMOPHILUS AND LACTOBACILLUS DELBRUECKII SUBSP. BULGARICUS. Journal of Industrial Microbiology and Biotechnology. 37:65-69. Interpretive Summary: Listeria are pathogenic bacteria that may contaminate dairy foods and cause outbreaks of food borne disease. Pediococci which are food grade lactic acid bacteria used in meat fermentations produce natural antilisterial peptides known as pediocins and may be useful as natural biopreservatives in listeria control. However, pediococci cannot ferment lactose and consequently do not grow well in a milk environment. In this study, we tested the capacity of pediococci for growth and pediocin production when cocultured in milk with selected streptococci and lactobacilli which are standard yogurt starter cultures. The results showed that the Streptococcus component of the culture mix was the key to creating favorable conditions for Pediococcus growth and the production of pediocin in amounts that was adequate to control the growth of listeria in fermented milk and during storage under refrigeration conditions. The capacity of pediococci for producing the antilisterial bacteriocin in fermented milk products broadens the range of applications of these cultures in the food industries.
Technical Abstract: The production of pediocin in milk by Pediococcus acidilactici was evaluated in co-culture with the dairy fermentation cultures Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, and Lactococcus lactis subsp. lactis. The cultures were tested singly or in different combinations in milk (0% or 2% fat content) during incubation at 42°C for up to 10 h. Cell-free milk samples were prepared every 60 min and tested for bacteriocin activity against Listeria monocytogenes. Pediocin production was not detectable when P. acidilactici was used alone or in co-culture with lactococci. When P. acidilactici was grown for 8 h in combination with the yogurt starter cultures S. thermophilus and Lb. delbrueckii subsp. bulgaricus, the concentration of pediocin produced reached 3,200 units mL-1. Pediococci could be included as adjuncts in traditional yogurt culture mixes consisting of S. thermophilus and Lb. delbrueckii subsp. bulgaricus to provide the additional benefit of protecting fermented dairy foods from listerial contamination.