Mesophilic fermentative hydrogen production from sago starch-processing wastewater using enriched mixed cultures

Biohydrogen (bioH(2)) production from starch-containing wastewater is an energy intensive process as it involves thermophilic temperatures for hydrolysis prior to dark fermentation. Here we report a low energy consumption bioH(2) production process with sago starch powder and wastewater at 30 degrees C using enriched anaerobic mixed cultures. The effect of various inoculum pretreatment methods like heat (80 degrees C, 2 h), acid (pH 4, 2.5 N HCl, 24 h) and chemical (0.2 g L-1 bromoethanesulphonic acid, 24 h) on bioH(2) production from starch powder (1% w/v) showed highest yield (323.4 mL g(-1) starch) in heat-treatment and peak production rate (144.5 mL L-1 h(-1)) in acid-treatment. Acetate (1.07 g L-1) and butyrate (1.21 g L-1) were major soluble metabolites of heat-treatment. Heat-treated inoculum was used to develop mixed cultures on sago starch (1% w/v) in minimal medium with 0.1% peptone-yeast extract (PY) at initial pH 7 and 30 degrees C. The effect of sago starch concentration, pH, inoculum size and nutrients (PY and Fe ions) on batch bioH(2) production showed 0.5% substrate, pH 7, 10% inoculum size and 0.1% PY as the best H-2 yielding conditions. Peak H-2 yield and production rate were 412.6 mL g(-1) starch and 78.6 mL L-1 h(-1), respectively at the optimal conditions. Batch experiment results using sago-processing wastewater under similar conditions showed bioH(2) yield of 126.5 mL g(-1) COD and 456 mL g(-1) starch. The net energy was calculated to be +2.97 kJ g(-1) COD and +0.57 kJ g(-1) COD for sago starch powder and wastewater, respectively. Finally, the estimated net energy value of +2.85 x 10(13) kJ from worldwide sago-processing wastewater production indicates that this wastewater can serve as a promising feedstock for bioH(2) production with low energy input. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.