Fermentative Hydrogen Production Process Research Articles

Sustainable biohydrogen production from lignocellulosic biomass sources - metabolic pathways, production enhancement, and challenges.

Hydrogen production from biological processes has been hailed as a promising strategy for generating sustainable energy. Fermentative hydrogen production processes such as dark and photofermentation are considered more sustainable and economical than other biological methods such as biophotolysis. However, these methods have constraints such as low hydrogen yield and conversion efficiency, so practical implementations still need to be made. The present review provides an assessment and feasibility of producing biohydrogen through dark and photofermentation techniques utilizing various lignocellulosic biomass wastes as substrates. Furthermore, this review includes information about the strategies to increase the productivity rate of biohydrogen in an eco-friendly and sustainable manner, like integration of dark and photofermentation techniques, pretreatment of biomass, genetic modification of microorganisms, and application of nanoadditives.

Corncob ash boosts fermentative hydrogen production from waste activated sludge

With the increasing demand for sustainable development, the recycling and utilization of wastes has received widespread attention. This study proposed a green method of using one waste, corncob ash, to boost microbial the production of hydrogen from another waste, waste activated sludge, during anaerobic fermentation. The corncob ash dosage and the fermentative hydrogen production was positively correlated, and the maximum production of hydrogen reached up to 46.8 ± 1.0 mL/g VS, which was about 3.5 times that of the control group without corncob ash dosage (17.0 ± 0.9 mL/g VS). Mechanistic studies found that corncob ash was beneficial to the solubilization, hydrolysis and acetogenesis processes involved in fermentative hydrogen production process. The microbial community analysis indicated that corncob ash enriched more hydrolytic microorganisms (e.g., Bacteroides sp. and Leptolinea sp.), and has less impact on acidifying microorganisms, compared to the control group. The strategy of using corncob ash to boost the production of hydrogen during anaerobic waste activated sludge fermentation proposed in this study might provide a new waste-control-waste paradigm, making sludge disposal and wastewater treatment more sustainable.

Simultaneous hydrogen production and decolorization of denim textile wastewater: kinetics of decolorizing of indigo dye by bacterial and fungal strains.

This study proposes the treatment and valorization of denim textile effluents through a fermentative hydrogen production process. Also, the study presents the decolorizing capabilities of bacterial and fungal isolates obtained from the fermented textile effluents. The maximum hydrogen production rate was 0.23L H2/L-d, achieving at the same time color removal. A total of thirty-five bacteria and one fungal isolate were obtained from the fermented effluents and screened for their abilities to decolorize indigo dye, used as a model molecule. From them, isolates identified as Bacillus BT5, Bacillus BT9, Lactobacillus BT20, Lysinibacillus BT32, and Aspergillus H1T showed notable decolorizing capacities. Lactobacillus BT20 reached 90% of decolorization using glucose as co-substrate after 11days of incubation producing colorless metabolites. Bacillus BT9 was able to utilize the indigo dye as the sole carbon source achieving a maximum decolorization of 60% after 9days of incubation and producing a red-colored metabolite. In contrast, Bacillus BT5 and Lysinibacillus BT32 exhibited the lowest percentages of decolorization, barely 33% after 16 and 11days of incubation, respectively. When Aspergillus H1T was grown in indigo dye supplemented with glucose, 96% of decolorization was reached after 2days. This study demonstrates the valorization of denim textile effluents for the production of hydrogen via dark fermentation with concomitant color removal.

Changes in microbial community during biohydrogen production using gamma irradiated sludge as inoculum

The changes in microbial community structures during fermentative hydrogen production process were investigated by analyzing 16S rDNA gene sequences using gamma irradiated sludge as inoculum. The experimental results showed that the microbial community structure of untreated sludge was very rich in diversity. After gamma irradiation, lots of species were inhibited, and species with high survival rates under radiation conditions became dominant. After fermentation, Clostridium butyrium and a sequence closely related to Clostridium perfringens ATCC 13124T (CP000246) became predominant, which were all common hydrogen producers. Microbial distribution analysis indicated that gamma irradiation was a good pretreatment method for enriching hydrogen-producing strains from digested sludge.

Hydrogen production from sugar beet molasses – a techno-economic study

Abstract Two-stage fermentative hydrogen production process comprising dark fermentation and photofermentation followed by gas upgrading is studied from the technical and economic points of view. It is assumed that a conceptual hydrogen plant is connected to a sugar factory so that technical sucrose solutions produced there (raw juice, thick juice and molasses) can be used as fermentation feedstocks. Process data needed for the study are based on the results of a recently completed research project and in the techno-economic assessment of hydrogen production, data acquired in the sugar industry are taken into account. A parametric study of the cost of hydrogen production from molasses shows that the total cost is highly sensitive to the capital and operating costs of the photofermentation stage. Prospects of cost reduction through further development of the two-stage fermentative process are discussed.

Metabolic flux network analysis of fermentative hydrogen production: Using Clostridium tyrobutyricum as an example

This study applies metabolic flux network analysis (MFA) to evaluate the metabolic flux of fermentative hydrogen production (FHP) with the use of Clostridium tyrobutyricum fed with either glucose or lactate/acetate as substrates. The MFA results suggest that hydraulic retention time (HRT) presents significant impact on hydrogen production from glucose. At HRT between 4 and 18 h, increase of HRT increased hydrogen production but decreased lactate production, while at HRT below 4 h decrease of HRT increased hydrogen production but decreased lactate production. The flux for lactate, butyrate and acetate seemed to affect H₂ production, due presumably to their impacts on the balance of NADH, ferredoxin and ATP. It is suggested that the MFA can be a useful tool to provide valuable information for optimization and design of the fermentative hydrogen production process.

Enhanced Biohydrogen Production From Wastewater And The Influence Of Operating Parameters

Enhancement of fermentative biohydrogen production was investigated both by treatment of microbial community and optimization of key parameters using the statistical methodology. The effect of temperature, initial pH, and feed to microorganisms (F/M) ratios, individually and interactively, 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 using a Box–Behnken design. The maximum hydrogen yield of 372.90 mL/g glucose was estimated at the temperature of 30.91°C, the initial pH of 8, and the F/M ratio of 0.25. The maximum hydrogen production rate of 6.55 mL/h was estimated at the temperature of 30.03°C, the initial pH of 7.27, and the F/M ratio of 1.79. The maximum substrate consumption efficiency of 98.8% was estimated at the temperature of 30.35 °C, the initial pH of 7.5, and the F/M ratio of 0.25. Total of volatile fatty acids (VFAs) and ethanol were analyzed at the end of all experiments and their changes with operational parameters were investigated. Modified Gompertz equation could describe the progress of cumulative hydrogen production in the batch tests of this study successfully.

Comparison of metabolic pathway for hydrogen production in wild-type and mutant Clostridium tyrobutyricum strain based on metabolic flux analysis

There has been a great interest in fermentative hydrogen production during recent decades. However, the low H2 yield associated with fermentative hydrogen production process continues to hinder its industrial application. It is delectable that a maximum 3.9 mol H2 per mol glucose was obtained in fed-batch fermentation mode with a butyric acid over-producing Clostridium tyrobutyricum mutant, which to our knowledge is the highest H2 yield ever got in the fermentation process with Clostridium sp. This study aimed to better understand the change of flux profile within the whole metabolic network and to conduct the metabolic flux analysis of fermentative hydrogen production. For the first time, we constructed a metabolic flux model for the anaerobic glucose metabolism of C. tyrobutyricum ATCC 25755, and revealed the internal mechanism responsible for the redistribution of the carbon flux in the mutant strain in comparison with the wide-type. The MFA methodology was used to study the fractional flux response to variations in operational pH, and revealed that pH was a significant operational parameter effecting on the fermentative hydrogen production process. Furthermore, the presence of NADH-ferredoxin oxidoreductase activity in this anaerobe was demonstrated. By measuring the activities of related enzymes in the biosynthesis pathway of hydrogen, we thus concluded that the increased specific activities of both NFOR and hydrogen-catalyzing enzyme (hydrogenase) would be attributed to the hydrogen over-producing.

Modeling of fermentative hydrogen production from sweet sorghum extract based on modified ADM1

The Anaerobic digestion model 1 (ADM1) framework can be used to predict fermentative hydrogen production, since the latter is directly related to the acidogenic stage of the anaerobic digestion process. In this study, the ADM1 model framework was used to simulate and predict the process of fermentative hydrogen production from the extractable sugars of sweet sorghum biomass. Kinetic parameters for sugars’ consumption and yield coefficients of acetic, propionic and butyric acid production were estimated using the experimental data obtained from the steady states of a CSTR. Batch experiments were used for kinetic parameter validation. Since the ADM1 does not account for metabolic products such as lactic acid and ethanol that are crucial during the fermentative hydrogen production process, the structure of the model was modified to include lactate and ethanol among the metabolites and to improve the predictions. The modified ADM1 simulated satisfactorily batch experiments although further modifications could be made in order to further improve the predictions for the hydrogenogenic process.

Electricity generation from mixed volatile fatty acids using microbial fuel cells

Fermentative hydrogen production, as a process for clean energy recovery from organic wastewater, is limited by its low hydrogen yield due to incomplete conversion of substrates, with most of the fermentation products being volatile fatty acids (VFAs). Thus, further recovery of the energy from VFAs is expected. In this work, microbial fuel cell (MFC) was applied to recover energy in the form of electricity from mixed VFAs of acetate, propionate, and butyrate. Response surface methodology was adopted to investigate the relative contribution and possible interactions of the three components of VFAs. A stable electricity generation was demonstrated in MFCs after the enrichment of electrochemically active bacteria. Analysis showed that power density was more sensitive to the composition of mixed VFAs than coulombic efficiency. The electricity generation could mainly be attributed to the portion of acetate and propionate. However, the two components showed an antagonistic effect when propionate exceeded 19%, causing a decrease in coulombic efficiency. Butyrate was found to exert a negative impact on both power density and coulombic efficiency. Denaturing gradient gel electrophoresis profiles revealed the enrichment of electrochemically active bacteria from the inoculum sludge. Proteobacteria (Beta-, Delta-) and Bacteroidetes were predominant in all VFA-fed MFCs. Shifts in bacterial community structures were observed when different compositions of VFA mixtures were used as the electron donor. The overall electron recovery efficiency may be increased from 15.7% to 27.4% if fermentative hydrogen production and MFC processes are integrated.

Metabolic flux analysis of hydrogen production network by Clostridium butyricum W5: Effect of pH and glucose concentrations

Fermentative hydrogen production by strict anaerobes has been widely reported. There is a lack of information related to metabolic flux distribution and its variation with respect to fermentation conditions in the metabolic production system. This study aimed to get a better understanding of the metabolic network and to conduct metabolic flux analysis (MFA) of fermentative hydrogen production by a recently isolated Clostridium butyricum strain W5. We chose the specific growth rate as the objective function and used specific H 2 production rate as the criterion to evaluate the experimental results with the in silico MFA. For the first time, we constructed an in silico metabolic flux model for the anaerobic glucose metabolism of C. butyricum W5 with assistance of a modeling program MetaFluxNet. The model was used to evaluate metabolic flux distribution in the fermentative hydrogen production network, and to study the fractional flux response to variations in initial glucose concentration and operational pH. The MFA results suggested that pH has a more significant effect on hydrogen production yield compared to the glucose concentration. The MFA is a useful tool to provide valuable information for optimization and design of the fermentative hydrogen production process.

Regulatory influence of CO 2 supplementation on fermentative hydrogen production process

This study presents an approach to enhance fermentative biohydrogen (H 2) production by improving the system buffering capacity through utilization of CO 2 generated from syngas. The experimental data substantiates the positive impact of CO 2 sparging on H 2 production process. Various CO 2 sparging times viz., 30, 60 and 120 s were evaluated on H 2 production and substrate degradation. Based on the optimum sparging time (60 s), experiments were further performed to study the influence of pH microenvironment (5, 6 and 7) on the process efficiency. Further the influence of periodic CO 2 sparging was also evaluated. Experimental data visualized a marked improvement on the overall process performance based on H 2 production and substrate degradation after sparging CO 2. Carbonic acid upon association/dissociation forms bicarbonates in the system. Alkaline condition helps to build up buffering nature, which resist fluctuations in pH even at higher VFA concentrations. Substrate degradation was effective during intermittent sparging at neutral conditions. CO 2 sparging directly effecting the bulk liquid environment of the system improves buffering nature which indirectly helps to maintain favorable microenvironment for biohydrogen production process.

Utilizing acid-rich effluents of fermentative hydrogen production process as substrate for harnessing bioelectricity: An integrative approach

Lower substrate degradation is one of the limiting factors associated with fermentative hydrogen production process. To overcome this, an attempt was made to integrate microbial fuel cell (MFC) as a secondary energy generating process with the fermentative hydrogen (H 2) production. The acid-rich effluents generated from the acidogenic sequential batch biofilm reactor (AcSBBR) producing H 2 by fermenting vegetable waste was subsequently used as substrate for bioelectricity generation in single chambered MFC (air cathode; non-catalyzed electrodes). AcSBBR was operated at 70.4 kg COD/m 3-day and the outlet was fed to the MFC at three variable organic loading rates. The final outlet from AcSBBR was composed of fermentative soluble acid intermediates along with residual carbon source. Experimental data illustrated the feasibility of utilizing acid-rich effluents by MFC for both additional energy generation and wastewater treatment. Higher power output (111.76 mW/m 2) was observed at lower substrate loading condition. MFC also illustrated its function as wastewater treatment unit by removing COD (80%), volatile fatty acids (79%), carbohydrates (78%) and turbidity (65.38%) effectively. Fermented form of vegetable wastewater exhibited higher improvement (94%) in power compared to unfermented wastewater. The performance of MFC was characterized with respect to polarization behavior, cell potentials, cyclic voltammetry and sustainable power. This integration approach enhanced wastewater treatment efficiency (COD removal, 84.6%) along with additional energy generation demonstrating both environmental and economic sustainability of the process.

Development of a fermentation-based process for biomass conversion to hydrogen gas

The production of hydrogen gas from biomass to meet the foreseen demand arising from the expected introduction of fuel cells is envisaged. Apart from the well-known gasification method, fermentative conversion can also be applied for this purpose. Two options of the latter method, that is, thermophilic fermentation and photofermentation can be combined in a two-stage process in which about 70% of hydrogen present in biomass is converted to gaseous form. It is expected that this process can be applied in decentralized, small-scale production units. The main stages of the fermentative hydrogen production process are the following: – biomass pretreatment to give fermentable feedstock and non-fermentables, – thermophilic fermentation in which fermentable feedstock is converted to hydrogen gas and organic acids, – photofermentation in which the organic acids are converted to hydrogen gas, – upgrading of hydrogen gas to meet product specification, – separation and treatment of non-fermentables. In order to develop a sustainable hydrogen production route based on fermentation, it is necessary to improve the existing knowledge of these process stages and to carry out process optimization studies. As a major step in this direction, the European research project HYVOLUTION has been organized under the 6th Framework Programme of the EU.

Insight into the dehydrogenase catalyzed redox reactions and electron discharge pattern during fermentative hydrogen production

Dehydrogenase (DH) activity associated with bio-electrochemical behavior was analyzed for the first time to understand the redox reactions involved in fermentative hydrogen (H 2) production process in concurrence with proton (H +) shuttling and electron (e −) discharge (ED) pattern. DH facilitates the availability of H + through redox reactions to make H 2. We have designed a comprehensive experimental study to evaluate the DH activity (H + shuttling) and ED to understand the biochemical process with the function of pH (5, 6, 7 and 8) and metabolic microenvironment [anaerobic, anoxic and aerobic (control)]. DH activity was observed to be higher during anaerobic operation suggesting the higher availability of H + and e − due to the inter-conversion of metabolites and the same was reflected in the voltammetry analysis. Higher H 2 production under anaerobic operation corroborated well with these findings. The DH activity associated with H + shuttling and ED was also correlated with the substrate degradation pattern.

High yield simultaneous hydrogen and ethanol production under extreme-thermophilic (70°C) mixed culture environment

Abstract The effect of pH and medium composition on extreme-thermophilic (70 °C) dark fermentative simultaneous hydrogen and ethanol production (process performance and microbial ecology) was investigated. Hydrogen and ethanol yields were optimized with respect to glucose, peptone, FeSO4, NaHCO3, yeast extract, trace mineral salts, vitamins, and phosphate buffer concentrations as well as initial pH as independent variables. A combination of low levels of both glucose (≤2 g/L) and vitamin solutions (≤1 mL/L) and high levels of initial pH (≥7), mineral salts solution (≥5 mL/L) and FeSO4 (≥100 mg/L) stimulated the hydrogen production, while high level of glucose (≥5 g/L) and low levels of both initial pH (≤5.5) and mineral salts solution (≤1 mL/L) enhanced the ethanol production. High yield of simultaneous hydrogen and ethanol production (1.58 mol H2/mol glucose combined with an ethanol yield of 0.90 mol ethanol/mol glucose) was achieved under extreme-thermophilic mixed culture environment. Results obtained showed that the shift of the metabolic pathways favouring either hydrogen or ethanol production was affected by the change in cultivation conditions (pH and medium composition). The mixed culture in this study demonstrated flexible ability for simultaneous hydrogen and ethanol production, depending on pH and nutrients formulation. The microorganisms involved could be regarded as simultaneous hydrogen/ethanol producers, as hydrogen and ethanol fermentation under all conditions was carried out by a group of extreme-thermophilic bacterial species related to Thermoanaerobacter, Thermoanaerobacterium and Caldanaerobacter.

Kinetic models for fermentative hydrogen production: A review

Abstract The kinetic models were developed and applied for fermentative hydrogen production. They were used to describe the progress of a batch fermentative hydrogen production process, to investigate the effects of substrate concentration, inhibitor concentration, temperatures, pH, and dilution rates on the process of fermentative hydrogen production, and to establish the relationship among the substrate degradation rate, the hydrogen-producing bacteria growth rate and the product formation rate. This review showed that the modified Gompertz model was widely used to describe the progress of a batch fermentative hydrogen production process, while the Monod model was widely used to describe the effects of substrate concentration on the rates of substrate degradation, hydrogen-producing bacteria growth and hydrogen production. Arrhenius model was used a lot to describe the effects of temperature on fermentative hydrogen production, while modified Han–Levenspiel model was used to describe the effects of inhibitor concentration on fermentative hydrogen production. The Andrew model was used to describe the effects of H + concentration on the specific hydrogen production rate, while the Luedeking–Piret model and its modified form were widely used to describe the relationship between the hydrogen-producing bacteria growth rate and the product formation rate. Finally, some suggestions for future work with these kinetic models were proposed.

Application of desirability function based on neural network for optimizing biohydrogen production process

A fractional factorial design was carried out to investigate the effects of temperature, initial pH and glucose concentration on fermentative hydrogen production by mixed cultures in batch tests and then the experimental data of substrate degradation efficiency, hydrogen yield and average hydrogen production rate were described by a neural network, based on which the simultaneous optimization of the three responses was performed by the method of desirability function. The analysis showed that the neural network could successfully describe the effects of temperature, initial pH and glucose concentration on the substrate degradation efficiency, hydrogen yield and average hydrogen production rate of this study. The maximum substrate degradation efficiency of 95.3%, hydrogen yield of 305.3 mL/g glucose and average hydrogen production rate of 23.9 mL/h were all obtained at the optimal temperature of 39.0 °C, initial pH of 7.0 and glucose concentration of 24.6 g/L identified by the method of desirability function based on a neural network. In sum, the method of desirability function based on a neural network was a useful tool to optimize several responses for fermentative hydrogen production processes simultaneously.

Optimization of fermentative hydrogen production process using genetic algorithm based on neural network and response surface methodology

A central composite design was carried out to investigate the effect of temperature, initial pH and glucose concentration on fermentative hydrogen production by mixed cultures in batch test. The modeling abilities of the response surface methodology model and neural network model, as well as the optimizing abilities of response surface methodology and the genetic algorithm based on a neural network model were compared. The results showed that the root mean square error and the standard error of prediction for the neural network model were much smaller than those for the response surface methodology model, indicting that the neural network model had a much higher modeling ability than the response surface methodology model. The maximum hydrogen yield of 289.8 mL/g glucose identified by response surface methodology was a little lower than that of 360.5 mL/g glucose identified by the genetic algorithm based on a neural network model, indicating that the genetic algorithm based on a neural network model had a much higher optimizing ability than the response surface methodology. Thus, the genetic algorithm based on a neural network model is a better optimization method than response surface methodology and is recommended to be used during the optimization of fermentative hydrogen production process.

Optimization and evaluation of fermentative hydrogen production and wastewater treatment processes using data enveloping analysis (DEA) and Taguchi design of experimental (DOE) methodology

The combined process efficiency with respect to fermentative hydrogen (H 2) production and wastewater treatment was evaluated in a series of batch experiments to enumerate the role of selected factors viz., origin of inoculum, pre-treatment, inlet pH and feed composition under anaerobic microenvironment using mixed culture. H 2 production and substrate degradation were found to depend significantly on the selected factors with individual conditions to achieve effective process performance. Significantly diverse operational conditions were observed for both H 2 production and substrate degradation with respect to process efficiency. However, while dealing with H 2 production in association with wastewater treatment, both the parameters are important and balancing the conditions for combined effective performance is critical. Data enveloping analysis (DEA) was applied to evaluate the combined system performance with respect to the two output parameters (H 2 production and substrate degradation) based on relative efficiency. Among various experimental combinations studied, those with untreated anaerobic mixed inoculum under acidophilic conditions (inlet pH 5.5) using simple wastewater as fermentative substrate illustrated combined process efficiency with respect to H 2 production (1.919 m mol H 2/day; 0.52 mol H 2/kg COD R-day) and substrate degradation (substrate degradation rate, 4.56 kg COD/m 3-day). DEA methodology provide the relative efficiency of the system by integrating two output parameters. Further, design of experimental methodology (DOE) by Taguchi approach was applied to enumerate the role of selected factors on the H 2 production and substrate degradation with the final aim of optimizing the process. By adapting the derived optimum conditions, the performance with respect to H 2 production and substrate degradation could be enhanced by three fold.