PEDIOCIN PRODUCTION BY PEDIOCOCCCUS ACIDILACTICI IN CO-CULTURE WITH YOGURT STARTER BACTERIA

Authors: Somkuti, George; Steinberg, Dennis

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/10/2006
Publication Date: 5/26/2006
Citation: Somkuti, G.A., Steinberg, D.H. 2006. Pediocin production by pediococccus acidilactici in co-culture with yogurt starter bacteria. (abstract) American Dairy Science Association. Paper No. T66.

Interpretive Summary: N/A

Technical Abstract: The direct production of the antilisterial bacteriocin pediocin in milk is not feasible since Pediococcus acidilactici poorly ferments lactose and prefers glucose for growth. Solutions to this problem have included the transfer of a lactose operon to pediococci from lactic bacteria and prehydrolysis of lactose with a suitable beta-galactosidase. In a different approach described here, the production of pediocin by P. acidilactici (PAF) was evaluated in co-culture with the yogurt starter cultures Streptococcus thermophilus (ST) and Lactobacillus delbrueckii subsp. bulgaricus (LDB), and the cheese starter culture Lactococcus lactis subsp. lactis (LLL). Maintenance medium for PAF and LDB was MRS broth, whereas ST and LLL were grown in tryptone-yeast extract-lactose broth. The cultures (50 ul each) were inoculated into milk (2% fat content) samples (10 ml) that were incubated at 37 deg C for up to 8 h. PAF was tested alone and in combination of ST, LDB and LLL. Samples were taken every 60 min, centrifuged for 10 min and following two-fold serial dilution, cell-free supernatants were tested for bacteriocin activity with Listeria innocua as the target organism. Pediocin production was not detectable when PAF was used alone or grown in co-culture with LLL. However, pediocin was apparently produced when PAF was co-cultured with either ST or LDB or in combination with the two yogurt starter cultures, and reached a maximum level estimated at 2,400 units/ml after 6 h of incubation. Since pediococci have been suggested as adjunct dairy starter cultures, the inclusion of pediocin-producing strains in starter mixtures consisting of ST and LDB strains may provide the additional benefit of serving as bioprotective agents to control listerial contamination in fermented dairy products.