Candida utilis can grow efficiently in a simple synthetic medium at low pH. The electron donor for yeast-mediated enantioselective bioreduction of acetophenone was ethanol, which was also used to dissolve the acetophenone to make a successful semi-fed-batch type reaction. NADH was added externally to assist the reduction. The pH of the culture was varied from 2.3 to 6.0 and the bioconversion temperature was controlled at 30 degrees C. In general, the productivity of yeast (PN) for the production of 1-phenylethanol was increased by raising the pH. The maximum PN was 4.17 mmol kg(-1) h(-1) at pH 6.0. However, the largest enantiomer excess (ee value) for the synthesis of S-(-)-1-phenylethanol wets 94.8 +/- 0.8% with the pH controlled at 5.0.