Decolorization by Caldicellulosiruptor saccharolyticus with dissolved hydrogen under extreme thermophilic conditions

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2015-02, Vol.262, p.847-853
• Main Authors: Shen, Nan, Huo, Ying-Chao, Chen, Jie-Jie, Zhang, Fang, Zheng, Hang, Zeng, Raymond J.
• Format: Article
• Language: English
• Subjects: Caldicellulosiruptor saccharolyticus; Decoloring; Dissolution; Dissolved hydrogen; Enzymatic decolorization; Equivalence; Ethyl alcohol; Extreme thermophilic; Fermentation; Hot springs; Hydrogenase; Nickel; Reduction
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2014.10.053

[Display omitted] •Caldicellulosiruptor saccharolyticus could degrade methyl orange effectively.•The decolorization happened enzymatically via dissolved hydrogen (DH).•The decolorization rate was positively related to DH and Ni–Fe hydrogenase.•Competition for hydrogen existed between decolorization and glucose fermentation. This study examined the decolorization ability of Caldicellulosiruptor saccharolyticus isolated from a thermal spring at the optimum growth temperature of 70°C. This study demonstrated, for the first time, C. saccharolyticus could effectively degrade methyl orange (MO) to 4-aminobenzenesulfonic acid (4-ABA) and N′,N-dimethyl-p-phenylenediamine (DPD) with dissolved hydrogen (DH) as the reducing equivalent. The decolorization reaction was catalyzed by Ni–Fe hydrogenase and the reaction rate was correlated positively to the concentration of DH. At high concentrations of DH the decolorization rates were 6.65 and 7.08mg/L/h, which decreased to 2.16 and 0.88mg/L/h after purging with N2. Furthermore, the addition of MO decreased the yield of ethanol via glucose fermentation owing to the limited reducing equivalents. We suggest the competition for hydrogen between the reduction of azo dyes and hydrogenotrophic methanogenesis processes might exist in mixed culture fermentation.