Continuous ethanol production by flocculating yeast in the fluidized bed bioreactor

Continuous fermentation by a highly flocculant strain of the yeast Saccharomyces cerevisiae was carried out in a tower fluidized-bed bioreactor. The synthetic and molasses media with a total sugar concentration of 17% (w/v) were used for fermentation. Different dilution rates were tested. Stable cell densities of 50 kg m-3 (dry weight) were maintained for all dilution rates. The ethanol productivity was increasing linearly with dilution rates up to 15-20 kg m-3 h-1. Aeration of the culture stabilized flocculating activity and viability of yeast and also permitted long-term operation of the bioreactor.