A Modification of Henrici's Vegetable-Juice Sporulation Medium for Yeasts

Abstract

The contents of one can (designated as containing 1 pint, 2 fluid ounces) of the mixed juice from 8 vegetables ("V-8", Standard Brands) is adjusted to pH 6.8 with KOH. One-half of a cake of compressed yeast is dispersed in it, and the mixture is steamed for 10 min. to kill the yeast cells and liberate the acids which they possess. The medium is adjusted to pH 6.8 again and then added to an equal volume of hot dist. water containing 4% of melted agar. The 2 solns. are mixed, then bottled or tubed, and sterilized for 15 min. at 15 pounds'' pressure. Unnecessary heating is avoided. The medium is freshly slanted not more than 8 hrs. before use. The entire surface of the slant is lightly inoculated from a 24-hr. culture grown on a yeast extract-malt extract slant at approx. 28[degree]C. The sporulation cultures are incubated at 24-25 [degree]C. Good sporulation of species of Hansenula, Zygohansenula, Pichia, and Zygopichia usually occur within 3 days, of Saccharomyces and Zygosaccharomyces at 5 to 7 days, and of Debaryomyces at 5 to 20 days.