Integration of ethanol removal using carbon nanotube (CNT)-mixed membrane and ethanol fermentation by self-flocculating yeast for antifouling ethanol recovery

Bioethanol is a renewable biofuel that has a strong inhibitory effect on cells in bioethanol fermentation by yeast. In this study, carbon nanotube (CNT)-mixed polydimethylsiloxane (PDMS) membranes were used for ethanol recovery from model solutions as well as for fermentation by self-flocculating yeast. Imbedding CNTs into the PDMS membrane led to enhanced ethanol recovery, with a maximum total flux of 128.7 g/m(2) h and an ethanol titer of 615.1 g/L in permeate. The CNTs can provide a flexible route for ethanol transport through the inner tubes or along the smooth surface. In fed-batch fermentation incorporating pervaporation, 112.3 g/L of ethanol was produced with an overall ethanol productivity and yield of 2.23 g/L h and 0.45 g/g, respectively. The membrane produced a highly concentrated condensate containing 400.3-487.5 g/L of ethanol. Furthermore, as yeast flocs can be throttled down in the bioreactot, self-flocculating yeast can be used to prevent membrane fouling induced by cell adsorption on the membrane. Therefore, the CNT-mixed membrane coupled with ethanol fermentation by self-flocculating yeast not only reduces ethanol-mediated inhibition of Cells but also saves the production cost because of the reduced fouling risk. Thus, this combination approach has potential in industrial bioethanol production for long-time operation. (C) 2016 Elsevier Ltd. All rights reserved.