Production of Bioethanol by Zymomonas Mobilis in High-gravity Extractive Fermentations

Azilah, Ajit and Ahmad Ziad, Sulaiman and Chisti, Yusuf (2017) Production of Bioethanol by Zymomonas Mobilis in High-gravity Extractive Fermentations. Food and Bioproducts Processing, 102. pp. 123-135. ISSN 0960-3085. (Published)

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Continuous removal of ethanol during production by the anaerobic bacterium Zymomonas mobilis mitigated ethanol inhibition. Ethanol inhibited its own production at a concentration of >20 g L−1. Ethanol productivity was enhanced by continuous in situ extraction with water-immiscible organic solvents. Several solvents were evaluated for biocompatibility with Z. mobilis and the ability to extract ethanol from a batch fermentation. In situ batch extractive fermentations were carried out in a 2-L stirred bioreactor (1:1 volume ratio of solvent and fermentation broth) with an optimal glucose concentration of 150 g L−1, 35 °C, and an agitation speed of 150 rpm. Oleyl alcohol, iso-octadecanol and 2-octyl-1-dodecanol were the three solvents that were most compatible with Z. mobilis. With these solvents, the cell viability relative to control (no solvent) was 1.48 ± 0.40, 1.03 ± 0.18 and 1.05 ± 0.07, respectively, after two days of exposure. All solvents tested improved the final biomass concentration, the glucose consumption and ethanol production relative to control, but iso-octadecanol was clearly the most effective solvent. Using iso-octadecanol, the maximum ethanol concentration of 75 ± 3 g L−1 was attained. This was nearly 1.25-fold that of the control fermentation. For this solvent, the ethanol yield on glucose was 0.485 ± 0.005 g g−1 compared to a yield of 0.468 ± 0.005 g g−1 for the control culture.

Item Type: Article
Uncontrolled Keywords: Solvent extraction; Zymomonas mobilis; Bioethanol; Ethanol; Fermentation; Extractive fermentation
Subjects: T Technology > TP Chemical technology
Faculty/Division: Faculty of Chemical & Natural Resources Engineering
Depositing User: Mrs. Neng Sury Sulaiman
Date Deposited: 24 Feb 2017 07:01
Last Modified: 30 Jan 2018 02:58
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