CONCENTRATION AND RECOVERY OF THE BACTERIOCIN NISIN FROM LACTOCOCCUS-LACTIS SUBSP LACTIS

This investigation compared various techniques to concentrate and reco ver nisin from Lactococcus lactis cells, Centrifugation, combined with pH manipulation, was initially investigated as it is known that nisin will adsorb to producer cells at pH 6.5 and desorb at pH less than or equal to 3.0. Unfortunately, centrifugation stripped producer cells o f nisin even at pH 6.5; therefore a milder separation process (microfi ltration) was evaluated, Results using a medium (LTB) containing pepto ne, tryptone, yeast extract, NaCl, Na2HPO4 and glucose demonstrated th at nisin could be at least partially concentrated with cells via micro filtration, However, when a filtered stillage-based medium was used, n isin production was boosted to levels which exceeded the holding capac ity of producer cells, resulting in release of nisin from cells at pH 6.5, Since it appears unfeasible to use producer cells for nisin recov ery, an alternative may be to separately immobilize cells/ fragments i n a re-usable column to act as a 'resin' to adsorb nisin, Microfiltrat ion could then be used to release nisin from cells, with nisin recover ed by passing the permeated material through the immobilized-cell colu mns at pH 6.5.