Depleted acid whey from fresh curd cheese production, from which lactoferrin and part of other proteins were previously removed, was used for cultivation of Lactococcus lactis IM 145, bacteriocin nisin Z producing strain. 2,5 % yeast extract was added into the medium in order to stimulate the growth. Bacteriocin active biomass was produced in three batch processes in a 2,5-L bioreactor. At the beginning of the experiment pH was adjusted to 6,5 and was not regulated during the process. Beside pH, optical density and antimicrobial activity against bacteriocin sensitive strain Latilactobacillus sakei subsp. sakei IM 108 were monitored during fermentation. Bacteriocin activity was the highest after 6 to 8 h, which coincided with the stationary phase of growth (cfu/mL). After the fermentation broth was centrifuged, the nisin was isolated from the supernatant by ultrafiltration, reverse phase high performance liquid chromatography and cation-exchange chromatography. Purity and functionality of fractions were analysed by SDS-PAGE and antimicrobial activity tests. Cation-exchange chromatography at pH 6,0 was found to be the most efficient method for the purificiation of nisin. We confirmed that acid whey is a suitable medium for the cultivation of nisin Z producing lactococci and thus showed a new way of its usage which could contribute to the reduction of waste from the dairy industry.
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