Efficient ethanol producing yeast Saccharomyces cerevisiae cannot produce ethanol from raw starch
directly. Thus the conventional ethanol production required expensive and complex process. In this
study, we developed a direct and efficient ethanol production process from high-yielding rice harvested
in Japan by using amylase expressing yeast without any pretreatment or addition of enzymes or nutrients.
Ethanol productivity from high-yielding brown rice (1.1 g/L/h) was about 5-fold higher than that
obtained from purified raw corn starch (0.2 g/L/h) when nutrients were added. Using an inoculum volume
equivalent to 10% of the fermentation volume without any nutrient supplementation resulted in ethanol
productivity and yield reaching 1.2 g/L/h and 101%, respectively, in a 24-h period. High-yielding rice was
demonstrated to be a suitable feedstock for bioethanol production. In addition, our polyploid amylaseexpressing
yeast was sufficiently robust to produce ethanol efficiently from real biomass. This is first
report of direct ethanol production on real biomass using an amylase-expressing yeast strain without
any pretreatment or commercial enzyme addition