EFFECTS OF SPORULATION MEDIA AND STRAIN ON THERMAL-RESISTANCE OF BACILLUS-CEREUS SPORES

Spores of Bacillus cereus strains ATCC 7004, ATCC 4342 and ATCC 9818 w ere produced in four sporulation media (Nutrient Agar supplemented wit h 1 ppm Mn2+, Fortified Nutrient Agar, Angelotti Medium and Milk Agar) and their percentages of sporulation and heat resistance parameters o btained in a wide temperature range were compared. In all conditions s tudied, high rates of sporulation were obtained. Clear differences amo ng D-values for spores produced in the four media were observed. The m edium which yielded the most resistant spores and the magnitude with w hich the sporulation medium affected D-values was different for each s train. z-Values of the three strains were not influenced by the medium used to obtain spores.