To prepare the medium containing sugars without the addi- tion of water, thick juice must be diluted by several-fold volumes of crude whey. Considering the actual operation, varied volume of crude whey may be supplied to plants manufacturing ethanol from sugar beet. The fermentation test was then conducted in 50 mL of a medium in which the sugar content was initially adjusted to 200 mg mL-1 by diluting thick juice with an appropriate volume of whey and water (Table 1). Fig. 1 shows the maximum concentration of ethanol synthesized by strains K. marxianus KD-15, K. marx- ianus NBRC 1963, and S. cerevisiae NBRC 0224 within 120 h of fermentation and the contents of residual sugars. Strain KD-
15 consumed most sugars and synthesized ethanol over
99 mg mL-1 in media with any dilution. Ethanol production by strains NBRC 1963 and NBRC 0224 was reduced in proportion to the volume of whey accompanied by an increase of residual sugars.