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In this work, effects of agitation speed, inoculum ratio, initial substrate concentraion and incubation temperature were investigated for anaerobic biohydrogen production. The most suitable parameters were determined as agitation speed 200 rpm (0 - 200 rpm), microorganism inoculum ratio 1:10 v/v (1:10 - 1:200 v/v), initial substrate concentration 32.4 g COD/L (10.8- 32.4 g COD/L) and temperature 37°C (28-37°C). Under these conditions, 1257 mL H2 production, 17.06 mL H2/g KOI yield and 6.441 mL H2/L maximum H2 production rate had been reached. In the case of an incubation temperature of 37°C, the lag phase was observed to be approximately 6.5 h independent of the initial substrate concentration. The relationship between substrate concentration and product formation was evaluated as reaction order of 1 for elementary reaction rate model, reaction rate constants were calculated as 6.5x10-5 min-1 and 7.92x10-5 min-1 for temperatures of 28°C and 37°C, respectively. Arrhenius model parameters, frequency factor and activation energy were calculated as 9.74x1034 min-1 and 229.20 kJ/mol respectively. Maximum H2 production rates, Michaelis constants (KS) and R2 values were calculated as 11.47 mL H2/L.min, 74.66 mL H2/L.min, 181.9 g COD/L, 447.7 g COD/L and 0.9458, 0.9505 for 28°C and 37°C temperatures, respectively. Using modified Gompertz model, all R2 values were obtained greater than 0.99, maximum H2 production potentials were found as 2.126 L H2/L, 2.777 L H2/L at 28°C and 37°C with 32.4 g COD/L, respectively. Maximum H2 production rate was reached as 15.250 mL H2/L.min at 37°C and 27 g COD/L initial substrate concentration. [ABSTRACT FROM AUTHOR]

In this work, effects of agitation speed, inoculum ratio, initial substrate concentraion and incubation temperature were investigated for anaerobic biohydrogen production. The most suitable parameters were determined as agitation speed 200 rpm (0 - 200 rpm), microorganism inoculum ratio 1:10 v/v (1:10 - 1:200 v/v), initial substrate concentration 32.4 g COD/L (10.8- 32.4 g COD/L) and temperature 37°C (28-37oC). Under these conditions, 1257 mL H2 production, 17.06 mL H2/g KOI yield and 6.441 mL H2/L maximum H2 production rate had been reached. In the case of an incubation temperature of 37°C, the lag phase was observed to be approximately 6.5 h independent of the initial substrate concentration. The relationship between substrate concentration and product formation was evaluated as reaction order of 1 for elementary reaction rate model, reaction rate constants were calculated as 6.5x10-5 min-1 and 7.92x10-5 min-1 for temperatures of 28°C and 37°C, respectively. Arrhenius model parameters, frequency factor and activation energy were calculated as 9.74x1034 min-1 and 229.20 kJ/mol respectively. Maximum H2 production rates, Michaelis constants (KS) and R2 values were calculated as 11.47 mL H2/L.min, 74.66 mL H2/L.min, 181.9 g COD/L, 447.7 g COD/L and 0.9458, 0.9505 for 28ºC and 37°C temperatures, respectively. Using modified Gompertz model, all R2 values were obtained greater than 0.99, maximum H2 production potentials were found as 2.126 L H2/L, 2.777 L H2/L at 28°C and 37°C with 32.4 g COD/L, respectively. Maximum H2 production rate was reached as 15.250 mL H2/L.min at 37°C and 27 g COD/L initial substrate concentration. [ABSTRACT FROM AUTHOR]

Hydrogen can be produced via dark and photo-fermentation using either single-stage or two-stage processes. The advantage of a two-stage system is that it is possible to separately optimize and control culture conditions for the dark and photo-fermentative bacteria. In the present study a mixture of starch and glucose was used as carbon source for the dark fermentation step. Response surface methodology (RSM) with a Box-Behnken design (BBD) was applied to the photo-fermentation stage for the optimization of key parameters: inoculum concentration ( Rhodopseudomonas palustris ), substrate concentration (dark fermentation effluent (DFE)) and pH. In this sequential two-stage system, the highest overall hydrogen yield (8.3 ± 0.1 mmol H 2 /gCOD), overall hydrogen production (1.62 mmol) and the photo fermentation yield (7.21 ± 0.2 mmol H 2 /gCOD) were achieved at inoculum of 9 mL (1.64 ± 0.7 × 10 8 cells), a DFE dilution of 2.5× and a pH of 7.5, which were center points of the design. 97% COD removal was achieved at the highest dilution of DFE (lowest concentration of carbon source) at pH 6.5. [ABSTRACT FROM AUTHOR]

Both dark and photo-fermentation can be used for biological hydrogen production; either performed separately, in two-stage systems, or in co-culture. A single stage process is less laborious and costly; however, the two types of microorganisms have different nutritional requirements requiring optimization of culture conditions. Here a response surface methodology (RSM) with a Box-Behnken design was used to optimize microorganism ratio and substrate and buffer concentrations, and to evaluate their interactive effects for maximization of hydrogen yield. Clostridium butyricum and Rhodopseudomonas palustris were grown on a potato starch/glucose base medium at 30 °C under continuous illumination (40 W m−2 light intensity). The highest hydrogen yield, 6.4 ± 1.3 mol H2/mol glucose, was obtained with a substrate concentration of 15 g/L, buffer concentration of 50 mM, and microorganism ratio of 3. The observed strong interaction between buffer and substrate concentration is most likely due to the need to optimize the pH for co-cultures. [ABSTRACT FROM AUTHOR]

Biological hydrogen production is under extensive investigation worldwide and has attracted the interest of researchers in a number of disciplines including the fundamental sciences, e.g., microbiology and biochemistry, and the applied sciences, e.g., chemical engineering. While the multidisciplinary approaches being used have been very fruitful in terms of advancing biohydrogen research, the data sets rapidly accumulating in the published literature are often difficult to compare due to the use of different units, or the incomplete description of experimental conditions. Here we review some of the common methods that are used in various aspects of biohydrogen research and suggest ways of reporting data that enable conversion to other units and comparison with similar research being carried out elsewhere. In addition, we have compiled in one place common abbreviations and definitions as well as useful physical/chemical constants and laws pertaining to hydrogen. Unlike other reviews that examine the results of specific studies, or describe the different systems being deployed and compare them, here we provide in one place for the first time a detailed listing and description of the up-to-date methods used in measurement and quantification of biohydrogen production. Useful conversion factors and physical constants are also given. • Different ways of reporting data resulting from biological hydrogen production. • General substrate consumption and product formation analysis in biohydrogen production. • Detailed measurement methods for light intensity and biomass. • Parameters specific to dark/photo fermentation and MECs delineated. • Physical/chemical constants and laws pertaining to hydrogen given in one place. [ABSTRACT FROM AUTHOR]

This study proposes that the on-line pH control via a model-based adaptive controller markedly improves the dark fermentative hydrogen production. According to the dynamic behavior of the dark fermentation process, pH, which rapidly declines with the beginning of the biogas production, should be precisely controlled around its optimal value in a narrow range. The success of on-line pH control was guaranteed by performing the preliminary simulation studies by experimental data obtained from dynamic analysis to determine ARMAX model order with Recursive Least Squares parameter estimation method and then to control the pH with Generalized Minimum Variance (GMV) controller. On-line control of pH at the optimal value of 6.0 during the 25 h dark fermentation process resulted in 5.4 times higher biogas production, 6.2 times higher biogas production potential, nearly doubled the duration of fermentation, and 18.4% biogas production rate increment in comparison with the uncontrolled pH case. Image 1 • First on-line System Identification and Generalized Minimum Variance Control (GMV) application on biohydrogen production. • Effective hydrogen production by dark fermentation with on-line pH control. • Higher biogas production was achieved compared to uncontrolled fermentation. • PH control nearly doubled the duration of fermentation. [ABSTRACT FROM AUTHOR]