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

Xue, Chuang, Wang, Zi-Xuan, Du, Guang-Qing, Fan, Li-Hai, Mu, Ying, Ren, Jian-Gang, Bai, Feng-Wu
Process biochemistry 2016 v.51 no.9 pp. 1140-1146
adsorption, batch fermentation, bioethanol, bioreactors, carbon nanotubes, ethanol, ethanol fermentation, ethanol production, fouling, pervaporation, production costs, risk, yeasts
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 128.7g/m²h and an ethanol titer of 615.1g/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, 112.3g/L of ethanol was produced with an overall ethanol productivity and yield of 2.23g/Lh and 0.45g/g, respectively. The membrane produced a highly concentrated condensate containing 400.3–487.5g/L of ethanol. Furthermore, as yeast flocs can be throttled down in the bioreactor, 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.