CHARACTERIZATION OF THE CULTURE FILTRATE OF KLUYVEROMYCES THERMOTOLERANS IFO-1778 AS A KILLER YEAST

Natural preservatives, especially those effective in the presence of N aCl, are desired. To develop such a natural preservative, we examined the killer effect against Z. rouxii of the culture filtrate of Kluyver omyces thermotolerans IFO 1778 strain. This strain was shown to have k iller activity against Z. rouxii in the presence of more than 4% NaCl. Its killer activity increased with the increase of NaCl concentration . Killer toxin of IFO 1778 was active in the range of pH 2 to 6 (optim um pH was 4). Killer activity was lost by heating at 40 degrees C for 15 min. Polyols had effect to stabilize killer activity. One percent c onc. of freeze-dried culture filtrate of koji medium inhibited the gro wth of Z. rouxii and delayed fermentation. While killer activity was n ot affected by proteases, it was increased by cellulase treatment.