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Issue 7, 2010
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Tandem production of levan and ethanol by microbial fermentation

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Abstract

Tandem production of levan and ethanol by microbial fermentation using sucrose substrate was investigated. The tandem process involves fermentation of Bacillus subtilis (natto) Takahashi in a sucrose medium to produce levan, separation of the levan product from glucose by-product by ultrafiltration and fermentation of the glucose remnant from levan production by Zymomonas mobilis to produce ethanol. After cultivation of B. subtilis (natto) Takahashi for 48 h, 56.0 ± 0.6 g l−1 of levan was produced in a medium containing 250 g l−1 sucrose, which was 45 ± 0.5% yield on available fructose. After removing the cells, the fermentation broth was concentrated by ultrafiltration through a membrane of 5 kDa cutoff. The filtrate which contained 179 ± 3 g l−1 of hexose was diluted, supplemented with yeast extract (5 g l−1), (NH4)2SO4 (1 g l−1), MgSO4·7H2O (0.5 g l−1), KH2PO4 (1 g l−1) and used for alcohol fermentation by Z. mobilis. Incubation of Z. mobilis in the medium containing glucose remnant at 30 °C, pH 5.5, 175 rpm for 120 h gave from 21.1 ± 0.3 to 26.5 ± 0.2 g l−1 of bio-ethanol depending on the dilution. The tandem process developed in this study is an eco-friendly process in that the sucrose substrate was fully utilized without wasting any by-products in the process; in addition, two invaluable environmentally-friendly biomaterials (levan and ethanol) were produced. Furthermore, the amount of alcohol required for levan recovery could be reduced to a quarter of that generally used in the conventional precipitation.

Graphical abstract: Tandem production of levan and ethanol by microbial fermentation

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Publication details

The article was received on 24 Nov 2009, accepted on 12 Apr 2010 and first published on 27 May 2010


Article type: Paper
DOI: 10.1039/B924765C
Green Chem., 2010,12, 1242-1247

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    Tandem production of levan and ethanol by microbial fermentation

    I. Shih, L. Chen, T. Wang, J. Wu and K. Liaw, Green Chem., 2010, 12, 1242
    DOI: 10.1039/B924765C

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