Yeast inoculum was obtained in 500-ml Erlenmeyer flasks with a medium volume of 200 ml, consisting of (grams per liter): glucose 30, yeast extract 5, (NH4)2SO4 10, KH2PO4 4.5, and MgSO4•7H2O 1, and initial pH of the media was adjusted at 5.0 (1 N HCl or 1 N NaOH).