RICE HULL ASH AND SILICIC-ACID AS ADSORBENTS FOR CONCENTRATION OF BACTERIOCINS

A model procedure has been developed for the rapid extraction of five bacteriocins (nisin, pediocin RS2, leucocin BC2, lactocin GI3, and ent erocin CS1) from concentrated freeze-dried crude culture supernatants by adsorption onto acid or alkaline rice hull ash (RHA) or silicic aci d (SA), Bacteriocins were adsorbed onto RHA or SA by a ps-dependent me thod and desorbed by decreasing the pH to 2.5 or 3.0 and heating at 90 degrees C for 5 min. The maximum adsorption and optimal pH range for different bacteriocins were as follows: nisin, 97% at pH 7.0; lactocin GI3, 94% at pH 6.0; pediocin RS2, 97% at pH 8.0 to 9.0; leucocin BC2, 88% at pH 9.0; and enterocin CS1, 94% at pH 5.0. The desorption level of lactocin GI3 or enterocin CS1 from the surfaces of both RHA and SA was 94%, while the desorption level of pediocin RS2 and leucocin BC2 was 50% or less. Nisin was desorbed readily from SA (91%) but not from RHA (50% or less). The adsorption of bacteriocins onto RHA and SA inc reased with the increasing concentration of bacteriocins. Analysis of the desorbed bacteriocins after dialysis and sodium dodecyl sulfate-16 % polyacrylamide gel electrophoresis showed a single band that gave a single inhibition zone when overlaid with Lactobacillus plantarum for detection of lactocin GI3, enterocin CS1, and nisin, RHA appears usefu l for extraction, concentration, and partial purification of the five bacteriocins.