The yeast-mediated acyloin condensation of benzaldehyde and pyruvic acid to form l-PAC occurs in a petroleum spirit solvent system at room temperature with moderate conversion (30%) and high enantioselectivity (86%ee) after 24 h. The addition of a small amount of ethanol (0.5% mL) to the reaction mixture inhibits the formation of the side product benzyl alcohol and increases the conversion to l-PAC. Conducting the reaction using C-13-labeled pyruvate indicated that the pyruvate was incorporated into the l-PAC and that the excess pyruvate was converted into ethanol. Conducting the reaction at 5degreesC results in similar conversion but higher enantioselectivity.