Monday, May 4, 2009
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Continuous bioethanol production in immobilized cells fermentor coupled with a pervaporation system
Isabella De Bari1, Daniela Cuna1, Valentina Stillo2, Federico Liuzzi1, and Vincenza Calabrò2. (1) Ter-Enebio, ENEA, ENEA CR TRISAIA, SS 106 Jonica, km 419+500, Rotondella (MT), Italy, (2) Dipartimento di Modellistica per l'Ingegneria, Università della Calabria, Via P. Bucci, Arcavacata di Rende (CS), Italy
In recent years, the research on bioethanol production from lignocellulosics has been mainly focused on the optimization of single conversion steps while less attention has been devoted to the process integration. In some cases, depending on the specific composition of the biomass processed, the final ethanol concentration in the broth could feebly reach the target of 4 wt% considered acceptable for a subsequent economically feasible distillation. Thus, one possible integration that might be beneficial for the process is the use of immobilized cells bioreactor faced with a continuous ethanol stripping module. This process configuration would offer several advantages: the use of immobilized cell bioreactors yields high productivities and the catalyst entrapment within the bioreactor is more suitable for continuous operations; the ethanol removal guarantees a reduced yeast stress and the production of more concentrated streams prior to the distillation.
In the present paper, the fermentation of glucose by Saccharomyces cerevisiae immobilized in alginate beads and the simultaneous pervaporation of the produced ethanol was investigated by using synthetic and real hydrolyzates. Preliminary results indicate that during continuous fermentation with initial cell densities of 2.6´107 cells/mL, ethanol productivities of 2.5-