Enhanced Bioethanol Production in Batch Fermentation by Pervaporation Using a PDMS Membrane Bioreactor

The integration of batch fermentation and membrane-based pervaporation process in a membrane bioreactor (MBR) was studied to enhance bioethanol production compared to conventional batch fermentation operated at optimum condition. For this purpose, a laboratory-scale MBR system was designed and fabricated. Dense hydrophobic Polydimethylsiloxane (PDMS) membrane was used for pervaporation. For fermentation, pure stock culture of Saccharomyces cerevisiae as microorganism and glucose as substrate were used. Compared to conventional batch fermentation, the MBR resulted in increase of cell density, decreasing ethanol inhibition, improved productivity and yield, and resumption of clean and concentrated ethanol. These effects can be attributed to the presence of membrane as a selective separation barrier for removal of ethanol from fermentation broth. The ethanol productivity increased at least by 26.83% over conventional batch fermentation; while concentrated ethanol was obtained in the condensate of cold-trap. Furthermore, ethanol concentration in permeated side was approximately 6 to 7 times higher than that of the broth. Some biological kinetic models were investigated for determination of growth rate kinetics in conventional and MBR batch fermentation. The best results were obtained using the Monod kinetic model.