Strain K7, which is used for industrial brewing of Japanese
sake, is capable of high-ethanol productivity and tolerance
compared with laboratory strains. To determine whether the
pulp hydrolysates inhibit yeast growth, fermentation tests were
performed using strain K7. High-ethanol yields and productivities
were observed when 5% and 10% pulp hydrolysates were fermented
with strain K7, while ethanol yield and productivity from
20% and 30% pulp hydrolysates were significantly lower (Table 2).
In contrast, all reference fermentations, where glucose was used
as substrate instead of cassava pulp hydrolysates, showed highethanol
yield and productivity even with high substrate
concentrations (Table 2). Thus, low performance from fermentation
with 20% and 30% pulp hydrolysates probably is due to
accumulation of inhibitory by-products from the hydrothermal
treatment [8].