Formation of dry-heat resistant Bacillus subtilis var. niger spores as influenced by the composition of the sporulation medium.

Bacillus subtilis var. niger spores were produced on 20 different media. The spore yield from each medium and the dry-heat resistance at 160 C of the different spore populations were determined. The yield varied with a factor of 10(6) and the variation in D 160-value was about 10-fold (less than 20 S-190 S). A "synthetic" medium producing a high yield of spores with high dry-heat resistance was formulated. The concentrations of glucose, sucrose and calcium were found to be critical.