Continuous Acetone-Butanol-Ethanol (ABE) Fermentation with in Situ Solvent Recovery by Silicalite-1 Filled PDMS/PAN Composite Membrane

The pervaporation (PV) performance of a thin-film silicalite-1 filled PDMS/PAN composite membrane was investigated in the continuous acetone-butanol-ethanol (ABE) production by a fermentation-PV coupled process. Results showed that continuous removal of ABE from the broth at three different dilution rates greatly increased both the solvent productivity and the glucose utilization rate, in comparison to the control batch fermentation. The high solvent productivity reduced the acid accumulation in the broths because most acids were reassimilated by cells for ABE production. Therefore, a higher total solvent yield of 0.37 g/g was obtained in the fermentation-PV coupled process, with a highly concentrated.. condensate containing 89.11-160.00 g/L, ABE. During 268 h of the fermentation-PV coupled process, the PV membrane showed a high ABE separation factor of more than 30 and a total flux of 486-710 g/m(2)h. Membrane fouling was negligible for the three different dilution rates. The solution-diffusion model, especially the mass transfer equation, was proved to be applicable to this coupled process.