Intensification of lignocellulosic bioethanol production process using continuous double-staged immersed membrane bioreactors

Abstract

Processing complexities associated with different lignocellulosic bioethanol production stages have hindered reaching full commercial capacity. Therefore, in this study efforts were made to remediate some issues associated with hydrolysis and fermentation, by the integration of immersed membrane bioreactors (iMBRs) into lignocellulosic bioethanol production process. In this regards, double-staged continuous saccharification-filtration and co-fermentation-filtration of wheat straw slurry was conducted using iMBRs at filtration fluxes up to 51.0 l.m^-2.h^-1 (LMH). The results showed a stable long-term (264 h) continuous hydrolysis-filtration and fermentation-filtration with effective separation of lignin-rich solids (up to 70% lignin) from hydrolyzed sugars, and separation of yeast cells from bioethanol stream at an exceptional filtration performance at 21.9 LMH. Moreover, the effect of factors such as filtration flux, medium quality and backwashing on fouling and cake-layer formation was studied. The results confirmed the process intensification potentials of iMBRs in tackling commonly faced technical obstacles in lignocellulosic bioethanol production.

Keywords: Immersed membrane bioreactors; Lignocellulosic bioethanol; Membrane fouling; Process intensification.