The feedstock used in this study, sugar beet raw juice and thick
juice, were provided by Hokkaido Bioethanol Co., Ltd. (Sapporo City,
Japan). The harvested and washed sugar beet roots were mechanically
sliced into cossettes; these were then used for sugar extraction
using hot water at 70 C. The obtained solution was raw juice.
The raw juice was clarified by liming followed by saturation with
CO2. The generated solid was filtrated, and the clear liquid portion
was then concentrated in a multi-effect evaporator into thick juice.
The raw juice was stored at 20 C, and it was thawed at 60 C
before use. The thick juice was stored at 4 C. In total, five plastic
containers of the raw juice and two plastic containers of the thick
juice were sent to our laboratory via frozen chain. Table 1 shows the
representative values of the components of raw juice and thick
juice. Although sucrose was partly enzymatically hydrolyzed to
glucose and fructose, it was acceptable because all of them were
fermentable.
The flocculating yeast S. cerevisiae strain KF-7, which was constructed
by protoplast fusion of the flocculating yeast strain IR-2
and the thermotolerant yeast strain EP-1 [16], was used in this
study.