Dark fermentation of ground wheat starch for bio-hydrogen production by fed-batch operation

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Abstract Ground wheat solution was used for bio-hydrogen production by dark fermentation using heat-treated anaerobic sludge in a completely mixed fermenter operating in fed-batch mode. The feed wheat powder (WP) solution was fed to the anaerobic fermenter with a constant flow rate of 8.33 mL h−1 (200 mL d−1). Cumulative hydrogen production, starch utilization and hydrogen yields were determined at three different WP loading rates corresponding to the feed WP concentrations of 10, 20 and 30 g L−1. The residual starch (substrate) concentration in the fermenter decreased with operation time while starch consumption was increasing. The highest cumulative hydrogen production (3600 mL), hydrogen yield (465 mL H2 g−1 starch or 3.1 mol H2 mol−1 glucose) and hydrogen production rate (864 mL H2 d−1) were obtained after 4 days of fed-batch operation with the 20 g L−1 feed WP concentration corresponding to a WP loading rate of 4 g WP d−1. Low feed WP concentrations (10 g L−1) resulted in low hydrogen yields and rates due to substrate limitations. High feed WP concentrations (30 g L−1) resulted in the formation of volatile fatty acids (VFAs) in high concentrations causing inhibition on the rate and yield of hydrogen production.