Heat‐Activation Kinetics of Endospores of Bacillus subtilisa

摘要

SUMMARYBacillus subtilisstrain 5230 endospores suspended in water at a concentration ofca.1 × 108spores per ml were heat‐activated at eight temperatures ranging from 5 to 94°C. The response was measured by plate count and recorded as the beat‐activated decimal fraction of the total viable count. The method for determining total viable count ineluded a medium containing CaCl2and Na2dipicolinate. This medium enumerated total viable populations, which were equivalent to total direct microscopic counts, without the usual beat‐treatment requirement. A method was developed to evaluate the contribution by the plate‐count incubation to the total heat treatment. The exposure times were corrected to compensate for the incubation heat treatment. The heat‐activation response was obtained throughout the entire range of test temperatures; however, the exposure time required to achieve the response was extended as temperature was decreased. The logarithm of the rate of heat activation was related to the test temperature, i.e., at a lower temperature, a longer time was required for the response. The thermo‐dynamic properties for the system were: ΔH‡= 27.9 keal; ΔF‡= 25.1–26.4 kcal;