Search

Abstract: The inhibitory effect of added ethanol, acetic acid, propionic acid and butyric acid on fermentative hydrogen production by mixed cultures was investigated in batch tests using glucose as substrate. The experimental results showed that, at 35°C and initial pH 7.0, during the fermentative hydrogen production, the substrate degradation efficiency, hydrogen production potential, hydrogen yield and hydrogen production rate all trended to decrease with increasing added ethanol, acetic acid, propionic acid and butyric acid concentration from 0 to 300mmol/L. The inhibitory effect of added ethanol on fermentative hydrogen production was smaller than those of added acetic acid, propionic acid and butyric acid. The modified Han–Levenspiel model could describe the inhibitory effects of added ethanol, acetic acid, propionic acid and butyric acid on fermentative hydrogen production rate in this study successfully. The modified Logistic model could describe the progress of cumulative hydrogen production. [Copyright &y& Elsevier]

Abstract: The effect of temperature, initial pH and glucose concentration on fermentative hydrogen production by mixed cultures was investigated in batch tests, and the optimization of fermentative hydrogen production process was conducted by response surface methodology with a central composite design. Experimental results showed that temperatures, initial pH and glucose concentrations had impact on fermentative hydrogen production individually and interactively. The maximum hydrogen yield of 289.8mL/g glucose was estimated at the temperature of 38.6°C, the initial pH of 7.2 and the glucose concentration of 23.9g/L. The maximum hydrogen production rate of 28.2mL/h was estimated at the temperature of 37.8°C, the initial pH of 7.2 and the glucose concentration of 27.6g/L. The maximum substrate degradation efficiency of 96.9% was estimated at the temperature of 39.3°C, the initial pH of 7.0 and the glucose concentration of 26.8g/L. Response surface methodology was a better method to optimize the fermentative hydrogen production process. Modified logistic model could describe the progress of cumulative hydrogen production in the batch tests of this study successfully. [Copyright &y& Elsevier]

Abstract: The pretreatment of digested sludge by five methods (by acid, base, heat-shock, aeration and chloroform, respectively) was conducted in batch tests to evaluate and compare their suitability in the enrichment of hydrogen-producing bacteria. The experimental results showed that, at 35°C and initial pH 7.0, the hydrogen yields of the pretreated digested sludge were higher in comparison with the control test during the fermentative hydrogen production using glucose as the substrate. In all tests, for fermentative hydrogen production from glucose, the digested sludge pretreated by heat-shock could obtain the maximal hydrogen production potential, maximum hydrogen production rate, hydrogen yield, substrate degradation efficiency and biomass concentration, which were 215.4mL, 120.4mL/h, 221.5mL/g glucose, 97.2% and 2739mg/L, respectively. The final pH values in the liquid after fermentative hydrogen production in all tests were between 3.4 and 4.1. Heat-shock is an easy and practical pretreatment method for enriching hydrogen-producing bacteria from digested sludge. [Copyright &y& Elsevier]