Effect of Pepsin Inhibitor (S-PI) on the Growth of Rhodotorula glutinis

Sir: Pepsin inhibitor (S-PI), produced by Streptomyces naniwaensis, was found to be an acylpentapeptide with MW 643.1•`4) It in hibited not only pepsin but also acid proteases that are widely produced by various yeasts and fungi, by the formation of a protease-inhibitor complex. The authors intend to make use of S-PI, and therefore aerobically cultured an acid protease producing organism, Rho dotorula glutinis No. K-24,5) in the presence (6120μg per ml) or absence of S-PI at various temperatures for 92 hr in a medium