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Selection and application of nontoxic solvents in extractive ethanol fermentation

Lemos, D.A., Sonego, J.L.S., Boschiero, M.V., Araujo, E.C.C., Cruz, A.J.G., Badino, A.C.
Biochemical engineering journal 2017 v.127 pp. 128-135
batch fermentation, biocompatibility, bioreactors, castor oil, cell growth, culture media, ethanol, ethanol fermentation, ethanol production, oleic acid, solvents, sugarcane juice
In industrial ethanol production processes, high ethanol concentrations in the fermentation broth inhibit cell growth and reproduction, resulting in reduced productivity. Extractive fermentation can be used to reduce product inhibition by removing the ethanol from the fermentation broth. However, the lack of studies of nontoxic and inexpensive solvents that offer good extraction capacity still restricts the use of this technique. The objective of the present work was to evaluate ethanol production by extractive batch fermentation using nontoxic organic solvents, simulating industrial conditions. Biocompatibility and ethanol distribution coefficient (KDE) assays were performed to determine the ethanol extraction capacity of these solvents, using a simulated sugarcane juice fermentation medium. Liquid-liquid extractive fermentations with the solvents castor oil and oleic acid, amongst others selected, were performed in shake flasks and in a bench-scale bioreactor to evaluate the ethanol productivity at different scales and to compare the results with conventional fermentation. All the extractive fermentations with the two selected solvents presented higher performance, with ethanol productivity (PE) of up to 10.5kgm⁻³h⁻¹, which was 17% higher when compared to the conventional process without ethanol removal.