Exogenous anthrahydroquinone-2,6-disulfonate specifically increases xylose utilization during mixed sugar fermentation by Clostridium beijerinckii NCIMB 8052

The influence of a reduced extracellular electron shuttle (anthrahydroquinone-2,6-disulfonate, AH2QDS) on substrate utilization and H2 production was investigated at different glucose:xylose ratios using the fermentative culture Clostridium beijerinckii NCIMB 8052. Adding 250 μM AH2QDS increased the total substrate utilization by 23–66%, and specifically xylose utilization by 20–54% at glucose:xylose ratios of 1:1, 1:3 and 1:9. Adding 250 μM AH2QDS also increased the substrate utilization by 40–88% at all tested glucose:xylose ratios (which ranged from 1:9 to 9:1). Increasing AH2QDS concentrations from 250 μM to 2 mM increased xylose utilization (>99% xylose consumed) as well as cumulative hydrogen production during mixed sugar fermentation. The extent of glucose utilization was consistent amongst all tests, which was expected. However, hydroquinone amendment specifically increased the extent of xylose utilized irrespective of the starting glucose:xylose ratio. To the best of our knowledge this is the first report of 100% xylose utilization by C. beijerinckii NCIMB 8052 grown under mixed sugar conditions. These data demonstrate that the substrate utilization, particularly xylose utilization, can be manipulated by amending extracellular redox active compounds. This will improve pentose utilization during fermentation of hydrolyzates that result from pre-treatment of lignocellulosic materials with wild type (non-GMO) cultures.