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Abstract: Waste ground wheat was subjected to acid hydrolysis (pH = 3.0) at 90 °C for 15 min using an autoclave. The sugar solution obtained from acid hydrolysis was subjected to dark fermentation for hydrogen gas production after neutralization. In the first set of experiments, initial total sugar concentration was varied between 3.9 and 27.5 g L−1 at constant biomass (cell) concentration of 1.3 g L−1. Biomass concentration was varied between 0.28 g L−1 and 1.38 g L−1 at initial total sugar concentration of 7.2 ± 0.2 g L−1 in the second set of experiments. The highest hydrogen yield (1.46 mol H2 mol−1 glucose) and the specific formation rate (83.6 ml H2 g−1 cell h−1) were obtained with 10 g L−1 initial total sugar concentration. Biomass (cell) concentration affected the specific hydrogen production rate yielding the highest rate (1221 ml H2 g−1 cell h−1) and the yield at the lowest (0.28 g L−1) initial biomass concentration. The most suitable Xo /So ratio, maximizing the yield and specific rate of hydrogen gas formation was Xo /So  = 0.037. Dark fermentation of acid hydrolyzed ground wheat was found to be more beneficial as compared to simultaneous bacterial hydrolysis and fermentation. [Copyright &y& Elsevier]

Abstract: Batch dark fermentation experiments were performed to investigate the effects of biomass and substrate concentration on bio-hydrogen production from acid hydrolyzed ground wheat at 55 °C. In the first set of experiments, the substrate concentration was constant at 20 g total sugar L−1 and biomass concentration was varied between 0.52 and 2.58 g L−1. Total sugar concentration was varied between 4.2 and 23.7 g L−1 in the second set of experiments with a 1.5 g L−1 constant biomass concentration. The highest cumulative hydrogen formation (582 mL, 30 °C, 1 atm), formation rate (5.43 mL h−1) and final total volatile fatty acid (TVFA) concentration (6.54 g L−1) were obtained with 1.32 g L−1 biomass concentration. In variable substrate concentration experiments, the highest cumulative hydrogen (365 mL) and TVFA concentration (4.8 g L−1) were obtained with 19.25 g L−1 initial total sugar concentration while hydrogen gas formation rate (12.95 mL h−1) and the yield (200 mL H2 g−1 total sugar) were the highest with 4.2 g L−1 total sugar concentration. [Copyright &y& Elsevier]

Abstract: Dark fermentation effluents of wheat powder (WP) solution containing different concentrations of volatile fatty acids (VFAs) were subjected to low voltage (1–3V) DC current to produce hydrogen gas. Graphite and copper electrodes were tested and the copper electrode was found to be more effective due to higher electrical conductivity. The effects of solution pH (2–7), applied voltage (1–3V) and the total VFA (TVFA) concentration (1–5gL−1) on hydrogen gas production were investigated. Hydrogen production increased with decreasing pH and became maximum at pH=2. Increases in applied voltage and the TVFA concentration also increased the cumulative hydrogen formation. The most suitable conditions for the highest cumulative hydrogen production was pH=2, with 3V applied voltage and 5g TVFA L−1. Up to 110ml hydrogen gas was obtained with 5gL−1 TVFA at pH=5.8 and 2V applied voltage within 37.5h. The highest energy efficiency (56%) was obtained with the 2V applied voltage and 10.85gL−1 TVFA. Hydrogen production by electrolysis of water in control experiments was negligible for pH>4. Hydrogen production by electrohydrolysis of VFA containing anaerobic treatment effluents was found to be an effective method with high energy efficiency. [Copyright &y& Elsevier]

Abstract: Three different Rhodobacter sphaeroides (RS) strains (RS–NRRL, RS–DSMZ and RS–RV) and their combinations were used for light fermentation of dark fermentation effluent of ground wheat containing volatile fatty acids (VFA). In terms of cumulative hydrogen formation, RS–NRRL performed better than the other two strains producing 48mlH2 in 180h. However, RS–RV resulted in the highest hydrogen yield of 250mlH2 g−1 TVFA. Specific hydrogen production rate (SHPR) with the RS–NRRL was also better in comparison to the others (13.8mlH2 g−1 biomassh−1). When combinations of those three strains were used, RS–RV+RS–DSMZ resulted in the highest cumulative hydrogen formation (90mlH2 in 330h). However, hydrogen yield (693mlH2 g−1 TVFA) and SHPR (12.1mlH2 g−1 biomassh−1) were higher with the combination of the three different strains. On the basis of Gompertz equation coefficients mixed culture of the three different strains gave the highest cumulative hydrogen and formation rate probably due to synergistic interaction among the strains. The effects of initial TVFA and NH4–N concentrations on hydrogen formation were investigated for the mixed culture of the three strains. The optimum TVFA and NH4–N concentrations maximizing the hydrogen formation were determined as 2350 and 47mgL−1, respectively. [Copyright &y& Elsevier]

Abstract: Powdered wheat solution was fermented batchwise for bio-hydrogen production using heat-treated anaerobic-acidogenic sludge as the inoculum at initial pH of 7.0 and temperature of 37°C. In order to determine the most suitable wheat powder (WP) and cell concentrations yielding the highest hydrogen formation, initial WP concentration was varied between 5 and 30gL−1 at a constant initial biomass concentration (2.6gL−1). The initial biomass concentration was varied between 0.5 and 5.0gL−1 at constant WP concentration of 20gL−1 in another set of experiments. Cumulative bio-hydrogen formation, hydrogen yield and the formation rate were maximum at the WP concentration of 20gL−1. Higher WP concentrations resulted in lower fermentation performance probably due to substrate and product (VFA) inhibition. Similarly, hydrogen formation rate and the yield were maximum with a biomass concentration of 2.5gL−1. Higher biomass concentrations resulted in lower hydrogen yield and formation rates due to product inhibition. The optimum initial biomass/substrate ratio maximizing the hydrogen yield and formation rate was found to be 0.125g biomassg−1 WP. A kinetic model was developed for bio-hydrogen formation from powdered wheat starch and the constants were determined by regression analysis. [Copyright &y& Elsevier]

Abstract: The effects of C/N and C/P ratio on hydrogen yield and specific production rate were investigated in dark fermentation of wheat powder solution (WPS) by external addition of N and P since the wheat powder was N and P deficient. A Box–Wilson statistical experiment design approach was used. C/N ratio was varied between 20 and 200 while C/P ratio was between 50 and 1000. A quadratic response function was used to correlate the objective functions with the independent variables and the response function coefficients were determined by regression analysis. Hydrogen yield increased with increasing C/N and C/P ratios. Low nitrogen concentrations required low phosphorous contents for high hydrogen yields. A C/N ratio of 200 and C/P ratio of 1000 yielded the highest yield of at STP. SHPR also increased with increasing C/N and C/P ratios. Again the highest SHPR ( at STP) was obtained at C/N and C/P ratios of 200 and 1000, respectively. The C/N/P ratio maximizing the yield and formation rate of hydrogen was 100/0.5/0.1 . [Copyright &y& Elsevier]