Development of combined nanofiltration and forward osmosis process for production of ethanol from pretreated rice straw

Abstract

A membrane process combining nanofiltraion (NF) and forward osmosis (FO) was developed for the sugar concentration with the aim of high bio-ethanol production from the liquid fraction of rice straw. The commercial NF membrane, ESNA3, was more adequate for removal of fermentation inhibitors (such as acetic acid) than the FO membrane, whereas the commercial FO membrane, TFC-ES, was more adequate for concentration of the sugars than the NF membrane. The liquid fraction was subjected to the following process: NF concentration with water addition (NF_(+H2O))→enzymatic hydrolysis→FO concentration. This NF_(+H2O)-FO hybrid process generated a total sugar content of 107g·L^-1. Xylose-assimilating S. cerevisiae produced 24g·L^-1 ethanol from the liquid fraction that was diluted 1.5-fold and then concentrated by the NF_(+H2O)-FO hybrid process. The NF_(+H2O)-FO hybrid process has the potential for optimized ethanol production from pretreated lignocellulosic biomass.

Keywords: Bio-ethanol; Fermentation; Forward osmosis; Nanofiltration; Rice straw.