MEDIUM-INDUCED FRAGILITY OF SCHWANNIOMYCES

Schwanniomyces occidentalis has attracted interest because of its abil ity to metabolize starch and similar complex carbohydrates. Studies ha ve been undertaken, mostly using defined media, to ascertain condition s for optimal production and secretion of hydrolytic enzymes. Here we demonstrate the fragility of Schw. occidentalis in many defined media. We especially examined viability in YNB (Yeast Nitrogen Base) plus 1% glucose. Without phosphate supplementation, viability was routinely v ery low at stationary phase (usually less than 37%), whereas viability of stationary-phase cultures in phosphate-supplemented YNB usually ex ceeded 97%. The negative implications of having many, presumably perme abilized, dead cells present in assays for secretion of enzymes by liv ing yeast cells are discussed.