Liquid sporulation method and sporulation broth

A Geobacillus stearothermophilus sporulation broth for induction of spores, comprising:

• a combination of one or more types of metal ions, one or more types of mineral ions, one or more buffers, starch, animal-source peptone, and yeast extract dispersed in water, wherein:
• the one or more types of metal ions and the one or more types of mineral ions are from one or more dissociated inorganic salts provided in an amount falling in the range of 1 g/L to 20 g/L of the sporulation broth;
• the buffer is provided in an amount falling in a range of 1 g/L to 50 g/L of the sporulation broth;
• the starch is provided in an amount falling a range of 0.5 g/L to 20 g/L of the sporulation broth;
• and
• the animal-source peptone and the yeast extract are collectively provided in an amount falling in the range of 0.5 g/L to 30 g/L of the sporulation broth,
• wherein the one or more types of metal ions comprise manganese, zinc or both manganese and zinc,
• wherein the sporulation broth produces a spore population of Geobacillus stearothermophilus that is substantially free of vegetative cells at about 5.8×106 to about 1.7×108 CFU/mL.