Monday, April 29, 2013
Exhibit Hall
The recalcitrance of lignocelluloses makes it complicated to degrade into fermentable sugars and commonly results in the formation of toxic compounds. The final hydrolyzate therefore contains inhibitors such as acetic acid, furfural and lignin degradation products which can result in reduced or complete failure of the yeast to ferment the hydrolyzate to ethanol. One way to reduce the negative effect of the inhibitors is to increase the cell density inside the bioreactor and run the cultivation in a continuous mode. However, in order to run continuous cultivations at high dilution rate and high yeast density, cells have to be retained inside the reactor. In this study, a membrane bioreactor using a cross-flow membrane was applied to get a yeast density of up to 180 g L-1 in the reactor at a dilution rate of 0.5 h-1. The impact of furfural on the ethanol production in the continuous cultivation was investigated by adding furfural by pulse injection and by adding furfural to the inlet medium. Furfural was added to get furfural concentrations ranging from 0.8 to 21.8 g L-1. The yeast converted the furfural by in situ detoxification very rapidly at all pulse injections, even when adding 21.8 g L-1. Furfural addition to inlet medium also confirmed that the yeast could successfully produce ethanol even when up to 17.0 g L-1 furfural. These results demonstrated the high furfural resistance when using the applied membrane bioreactor system.