TPGY (Tryptone Peptone Glucose Yeast Extract) Broth is used to test the toxicity type of Clostridium botulinum cultures. Casein Hydrolysate and Peptic Digest of Animal Tissue provide amino acids, peptides, carbohydrates, vitamins, and minerals. Yeast Extract is a source of B-complex vitamins. Dextrose is the fermentable carbohydrate. Sodium Thyoglycollate is a reducing agent. Trypsin activates toxins of the non-proteolytic types, so presumptive non-proteolytic C. botulinum cultures are inoculated into TPGY Broth Base without Trypsin.