It was found in the preceding study that the strain that showed the highest radiation resistance among the strains washed out of dializers not yet sterilzed was Bacillus megaterium and the D-value of its spore was about 40 percent higher than that of B.pumilus ATCC27142 spore. In the present study, bundles of hollow fibers were inoculated with spores of both the B.megaterium and the B.pumilus and D-values of the spores were measured to be 0.42_7 and 0.16_9 Mrad, respectively. The dializer is consisted of several materials. Sterilization effect of gamma-ray irradiation is the least for hollow fibers, because they contain glycerin. It is concluded that 10^6 sterility assurance is achieved by setting the sterilization dose at 2.0 Mrad, about eight times of the D-value for the B.megaterium under the condition that the number of contaminants per product is less than 100.
