Effect of minerals on staphylococcal enterotoxin B production.

Raising the magnesium level from 0.4 to 1.5 mM in a medium containing only amino acids (2.08%), salts, and vitamins increased enterotoxin B production by Staphylococcus aureus S-6 by about 80%. The level of phosphates in the medium was lowered to one-tenth (to 2.87 mM) the original amount without adversely affecting growth and enterotoxin production. The optimum level of potassium was between 15 and 45 mM. Ammonium salts were not essential in the amino acid medium. Sufficient quantities of trace metals were already present. Revising the salt mixture according to the information obtained resulted in a doubling of the enterotoxin B production.