BIOENERGY AND BIOFUELS Anthrahydroquinone-2,6,-disulfonate (AH 2 QDS) increases hydrogen molar yield and xylose utilization in growing cultures of Clostridium beijerinckii Xiaofeng Ye & Eberhard Morgenroth & Xinyu Zhang & Kevin Thomas Finneran Received: 20 June 2011 / Revised: 15 August 2011 / Accepted: 6 September 2011 / Published online: 23 September 2011 # Springer-Verlag 2011 Abstract H 2 production and xylose utilization were inves- tigated using the fermentative culture Clostridium beijer- inckii NCIMB 8052. Adding anthrahydroquinone-2,6- disulfonate (AH 2 QDS) increased the extent of xylose utilization by 56% and hydrogen molar yield by 24–37%. Enhanced hydrogen molar yield correlated with increased xylose utilization and increases in the acetate/butyrate product ratio. An electron balance indicated that AH 2 QDS shifted the electrons from the butyric acid pathway (NADH-dependent pathway) to the acetic acid pathway (non-NADH-dependent pathway), putatively creating a surplus of reducing equivalents that were then available for hydrogen production. These data demonstrate that hydrogen yield and xylose utilization can be manipulated by amending redox active molecules into growing cultures. This will impact biohydrogen/biofuel production by allow- ing physiological manipulations of growing cells for increased (or decreased) output of selected metabolites using amendments that are not consumed during the reactions. Although the current yield increases are small, they suggest a target for cellular alterations. In addition, increased xylose utilization will be critical to the fermentation of pretreated lignocellulosic feedstocks, which may have higher xylose content. Keywords Hydrogen production . Hydrogen molar yield . Xylose utilization . Electron shuttling compounds Introduction A number of substrates have been investigated for fermentative hydrogen production including defined carbo- hydrates (mainly glucose and sucrose) (Kotsopoulos et al. 2006; Lee et al. 2008; Lee and Rittmann 2009; Lin et al. 2007; Skonieczny and Yargeau 2009), undefined waste materials such as lignocellulosic biomass (Kapdan and Kargi 2006; Lalaurette et al. 2009; Levin et al. 2009), and agricultural wastes (Duerr et al. 2007; Kapdan and Kargi 2006; Vijayaraghavan et al. 2007). Lignocellulosic biomass cannot be efficiently fermented by most industrial micro- organisms and needs to be pretreated (Kumar et al. 2009). Glucose and xylose are the two most abundant monomers resulting from lignocellulose pretreatment (Kumar et al. 2009; Ren et al. 2009). Xylose is also the second most abundant carbohydrate in agricultural waste (Temudo et al. 2009). Hexose molecules such as glucose are effectively fermented by various industrial microorganisms (i.e., Saccharomyces cerevisiae, Clostridium acetobutylicum) to generate bioenergy carriers (e.g., bioethanol) at high yields Electronic supplementary material The online version of this article (doi:10.1007/s00253-011-3571-1) contains supplementary material, which is available to authorized users. X. Ye : X. Zhang Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA E. Morgenroth ETH Zürich, Institute of Environmental Engineering, 8093 Zürich, Switzerland E. Morgenroth Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland K. T. Finneran (*) Department of Environmental Engineering and Earth Science, Clemson University, Anderson, SC 29625, USA e-mail: ktf@clemson.edu Appl Microbiol Biotechnol (2011) 92:855–864 DOI 10.1007/s00253-011-3571-1