Screening of pyruvate-producing yeast and effect of nutritional conditions on pyruvate production.

Abstract

To find a yeast strain that can overproduce pyruvate and to investigate the effect of nutrients on pyruvate production. Trichosporon cutaneum PD70, a yeast strain that can overproduce pyruvate, was isolated from shake-flask cultures of 132 yeast strains. Pyruvate was measured by the HPLC or DNP method (see Materials and methods). Pyruvate production reached approximately 30.0 +/- 1.0 g l(-1) in basal fermentation medium. Different nutrient supplements had great effects on pyruvate production. Some of the conditions that gave the highest yield are described. Exogenous thiamine supplement caused a decrease in pyruvate yield. Some amino acids, such as L-arginine, L-isoleucine and L-valine, caused a minor increase in pyruvate yield. Soybean peptone was the most suitable nitrogen source for pyruvate production. A glucose concentration of 15% in fermentation medium gave the highest yield (34.6 g l(-1)) and the highest yield against consumed glucose (0.429 g g(-1)). Nutrients have significant impacts on pyruvate production. As a pyruvate overproducing yeast strain independent of exogenous vitamins or amino acids, T. cutaneum PD70 provides an advantage for commercial pyruvate production.