Fermentation optimization of pediocin PD-1 production and a comparative study of the effect of pediocin PD-1, plantaricin 423 and nisin on biofilms of Oenococcus oeni

[摘要] ENGLISH ABSTRACT: Lactic acid bacteria are present in many foods and beverages and are used as starter cultures inthe production of a variety of fermented products. Many of these bacteria produce ribosomallysynthesized antimicrobial peptides (bacteriocins), which inhibit the growth of bacteria geneticallyclosely related to the producer cell. Since many of these target bacteria include foodbomepathogens such as Bacillus spp., Clostridium spp., Listeria spp., and Staphylococcus spp., thepractical importance of these peptides as food preservatives has been well documented and, in thecase of nisin and pediocin PA-I, commercially explored.The increased demand from health conscious consumers for foods with no chemicalpreservatives is putting renewed pressure on the producer to supply a clean and green product,but with the same or even an extended shelf life. Various research groups are screening lacticacid bacteria for production of novel broad-spectrum antimicrobial peptides or are exploring thepossibilities of altering known bacteriocins to inhibit Gram-negative bacteria, yeasts and molds.Pediocin PD-I, produced by Pediococcus damnosus NCFB 1832, belongs to the class Ilabacteriocins, i.e. heat-stable Listeria-active peptides, containing the YGNGV -consensus sequencein the N-terminal region. Little is known about the production and mode of activity of pediocinPD-I.In this study, production of pediocin PD-I was significantly increased by optimizing thegrowth medium, De Man Rogosa and Sharpe (MRS) broth. Addition of bacteriological peptone(1.7%, w/v), manganous sulphate (0.014%, w/v) and Tween 80 (3%, v/v), and lowering of the pHduring fermentation stimulated pediocin PD-I production and the level of organic acidsproduced. Maximum levels of bacteriocin activity were recorded at an initial pH of 6.7 in thelatter medium. Under these conditions the specific bacteriocin activity increased by a factor ofapproximately six after 55 h of fermentation.The effect of pediocin PD-I, plantaricin 423, produced by Lactobacillus plantarum 423, andcommercial grade nisin (Aplin and Barrett Ltd., Trowbrige, Wilts, England) was tested againstplanktonic cells of Oenococcus oeni and a biofilm of the cells established on stainless steelsurfaces identical to those used in wineries. After 5 h of treatment with 3000 AU (arbitraryunits )/ml of each bacteriocin, all planktonic cells of 0. oeni in a modified Chardonnay mustmedium were killed. All viable cells in the biofilm were killed after only 1 h in the presence of 3000 AU/ml of anyone of the bacteriocins. In addition, pediocin PD-I, plantaricin 423 and nisinremoved the biofilms from the surfaces and reduced the biomass either completely, as in the caseof pediocin PD-I, or by 58% and 50% as in the case of plantaricin 423 and nisin, respectively.These same results were recorded after 5 h of treatment with 3000 AU/ml in a modifiedChardonnay must medium.To our knowledge this is the first report of controlling biofilm formation of malolactic bacteriaon stainless steel surfaces with natural antimicrobial peptides. This implies that, apart from beingvery effective in controlling the cell numbers of free-living cells of 0. oeni, the threebacteriocins, especially pediocin PD-I, could also be used as natural sanitizers. The fact that theproduction and activity levels ofpediocin PD-I could be increased without genetically modifyingthe producer strain is an added advantage.

[发布机构] Stellenbosch University