Nutritional factors affecting the production of two bacteriocins from lactic acid bacteria on whey

The ability of Lactococcus lactis subsp. lactis CECT 539 and Pediococcus ac idilactici NRRL B-5627 to produce bacteriocins on both diluted and concentr ated whey was investigated in batch fermentations. Both strains produced th e higher amounts of biomass and bacteriocin titres on diluted whey. Luedeki ng and Piret expression was able to model the production of nisin, which wa s produced as a primary metabolite on both culture media. However, the pedi ocin production could not be typified in any case due to the negligible gro wth of P. acidilactici. Although the whey supported the growth and bacterio cin production by the two strains, both biomass and bacteriocin productions were lower than those obtained on MRS broth. The effect of total sugar, ni trogen, phosphorous and buffer concentrations on the production of nisin an d pediocin was studied in diluted whey using factorial experiments and empi rical modelling. The production of nisin was greatly inhibited by the incre ase in nitrogen, buffer, and to a lesser extent, sugar concentration in the medium, nevertheless, the used phosphorous source produced a light stimula tory effect on bacteriocin synthesis. In addition, the growth of Lc 1.04 wa s mainly affected by the nitrogen source used. On the other hand, pediocin was inhibited by the increase in buffer, phosphorous, and to a lesser degre e, by the sugar and nitrogen concentration. The inhibitory activity of pediocin disappeared almost totally after 15 min of treatment with trypsin, papain, subtilisin and pepsin. The activity of nisin was drastically reduced by treatment with trypsin, subtilisin and pep sin. Nevertheless, 50% of the initial activity was retained when nisin was treated with papain. Both bacteriocins showed the highest heat stability at acidic pH and short incubation times. (C) 2001 Elsevier Science B.V. All r ights reserved.