amount of more than 96% (based on mol concentration). The aver-age concentration of lactic acid, ethanol and acetate were 172.8,
28.4 and 131.1 mM. Thus, heterofermentation was still the domi-nant fermentative route when pH was increased to 5.0. In addition,
the ratio of acetate to ethanol changed from 0.5 at phase 3 of stage
1 to 5.0 at stage 2. The high amount of Bifidobacterium with ‘bifidus
pathway’ fermentation in the CSTR may be responsible for the
greatly increase of the ratio of acetate to ethanol.