Tuesday, May 1, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
The production of bioethanol from lignocellulosics is already transiting from the pilot to the commercial scale, however each step of the process is still under consideration to increase the efficiency and to low the production costs. From decade, the debate about if it is better to use the SSF or the SHF is still open. In general terms, SHF favors the enzymatic hydrolysis because it can be carried out at higher temperature (40-50 °C) where the enzymes are more active, while by SSF the enzymatic inhibition by the product is avoided, because the glucose is fermented into ethanol as soon as it is produced from cellulose or cellobiose. In this work, it has been used a patented bioreactor that allows to carry out simultaneously enzymatic hydrolysis and fermentation in the same vessel, but in two chambers which are separated by a porous diaphragm and kept at different temperature. In this way, the hydrolysis temperature is optimized in the hydrolytic chamber and the product inhibition is avoided in the fermentation chamber because the free glucose migrates from the first to the second chamber. Experiments have been carried out to compare the performances of the two-chambers bioreactor with those achievable in flask. The results have shown that the ethanol yield is increased of about 10%. Another worthwhile feature of the two-chambers bioreactor is that the residual lignin is confined in the hydrolysis chamber, so that the filtration of the fermentation broth, before or after the distillation, can be avoided.