Maximum Hydrogen Production Yield Research Articles

Elucidating the role of pH and total solids content in the co-production of biohydrogen and carboxylic acids from food waste via lactate-driven dark fermentation

Notwithstanding lactate-driven dark fermentation (LD-DF) can cope with inhibition issues associated with the over-proliferation of lactate producers, there is still a knowledge gap about the role of key operational parameters. In this study, the effect of pH and total solids (TS) content on the co-production of hydrogen and carboxylic acids, including medium-chain carboxylic acids (MCCAs), from food waste (FW) via LD-DF was investigated. A series of batch fermentations was conducted, first, without pH control, and then at fixed pH values of 5.5, 6.0 and 6.5, while maintaining constant the TS content at 5 %. It was observed that the higher the operational pH, the lower the accumulation of lactate and the higher the extent and rate of hydrogen production, sustaining a maximum hydrogen production yield and rate of 81 NmL/g VS fed and 9 NL/L-d, respectively, at pH 6.5. In a second series of batch tests, the TS content was adjusted to 5, 7.5 and 10 % while pH was set at 6.5. The highest hydrogen production performance (103 NmL/g-VS fed and 13.3 NL/L-d) was achieved at 7.5 % TS, which also resulted in the highest accumulation of MCCAs, particularly of caproate, with an associated titer of 8.7 g/L. Hydrogen production plateaued with the exhaustion of lactate regardless of the condition tested. Further assessment through biochemical methane potential tests showed that LD-DF effluents can be alternatively valorised into biogas. Overall, the results obtained confirmed the key role of pH and TS content in the LD-DF of FW and suggested that this non-conventional route may be an alternative approach to cope with lactate flux diverted toward undesirable non-hydrogen-producing metabolic pathways.

Synergistic enhancement of biohydrogen production by supplementing with green synthesized magnetic iron nanoparticles using thermophilic mixed bacteria culture

The production of biohydrogen can be improved by focusing on the nutrients needed by fermentative bacteria like iron. Iron reacts with the [Fe-Fe]-hydrogenase enzyme within the mixed bacteria culture for optimum hydrogen release. Iron nanoparticles (NPs) are attractive due to its unique properties and high reactivity. It can be produced through green synthesis, a more eco-friendly and relatively lower cost process, by using iron salt as precursor and green coconut shell extracted by deep eutectic solvent (DES) as reducing agent. The coconut shell extract consists of phytochemicals that help in producing polydisperse magnetic iron oxide nanoparticles at ∼75 nm in size. The addition of optimum concentration of 200 mg Fe/L magnetic iron NPs resulted in the maximum cumulative hydrogen production, glucose utilization and hydrogen yield of 101.33 mL, 9.12 g/L and 0.79 mol H2/mol glucose respectively. Furthermore, the kinetic analysis on Gompertz model using the optimum magnetic iron NPs concentration showed that the hydrogen production potential (P) and hydrogen production rate (Rm) increased to 50.69 mL and 3.30 mL/h respectively and the lag phase time reduced about 7.12 h as compared with the control experiment (0 mg Fe/L). These results indicated the positive effects of magnetic iron NPs supplementation on fermentative biohydrogen production of mixed bacteria culture and proved the feasibility of adding the magnetic iron NPs as the micronutrient for enhancement of such hydrogen production system.

Enhancing biohydrogen gas production in anaerobic system via comparative chemical pre-treatment on palm oil mill effluent (POME)

Biological hydrogen production using palm oil mill effluent (POME) as a carbon source through dark fermentation process has been suggested to be a promising bioenergy potential and enacts as alternative renewable energy source. Results have indicated that among various 1.5% (w/v) chemical pre-treatments (sodium hydroxide, NaOH; hydrochloric acid, HCl; sulphuric acid, H2SO4; phosphoric acid, H3PO4 and nitric acid, HNO3) on POME, using H3PO4 would generate maximum biohydrogen production of 0.193 mmol/L/h, which corresponded to a yield of 1.51 mol H2/mol TCconsumed with an initial total soluble carbohydrate concentration of 23.52 g/L. Among H3PO4 concentrations (1%–10%), the soluble carbohydrate content and the biohydrogen produced was highest and increased by 1.70-fold and 2.35-fold respectively at 2.5% (w/v), as compared to untreated POME. The batch fermentation maximum hydrogen production rate and yield of 0.208 mmol/L/h and 1.69 mol H2/mol TCconsumed were achieved at optimum pre-treatment conditions of pH 5.5 and thermophilic temperature (60 °C). This study suggests that chemical pre-treatment approaches manage to produce and improve the carbohydrate utilisation process further. Continuous fermentation in CSTR at the optimum conditions produce heightened 1.5-fold biohydrogen yield for 2.5% H3PO4 at 6 h HRT as compared to batch scale. Bacterial community via next-generation sequencing analysis at optimum HRT (6 h) revealed that Thermoanaerobacterium thermosaccharolyticum registered the highest relative frequency of 20.24%. At the class level, Clostridia, Bacilli, Bacteroidia, Thermoanaerobacteria, and Gammaproteobacteria were identified as the biohydrogen-producing bacteria in the continuous system. Insightful findings from this study suggest the substantial practical utility of dilute chemical pre-treatment in improving biohydrogen production.

Exploring the potential of Bacillus licheniformis AP1 for fermentive biohydrogen production using starch substrate: BBD based process parameter optimization

Performance of Bacillus licheniformis AP1 was first time examined for hydrogen production using starch substrate. The current study enhanced hydrogen yield by exploring the bacterium for various nutritional and environmental factors. The impact of three key variables such as pH (4.5, 5.5, 6.5 and 7.5), iron sulphate (0.01 mg/L, 0.05 mg/L, 0.25 mg/L, 1.25 g/L, 6.25 mg/L), and nickel chloride (0.0875 mg/L, 0.175 mg/L, 0.2 mg/L, 0.7 mg/L, 1.25 mg/L, 1.75 mg/L) were searched to study and analyze their individual effect on hydrogen production and yield. Primary optimization (by one factor at a time) of these factors gave us a range of optimal values which was further processed for multiple parameters optimization. A Box-Behnken Design (BBD) for three variables was used to attain the maximum yield of hydrogen production by using the optimized values of each variable. The interactive parameters were set as runs (from 1 run to 15 run) in each batch system using response surface methodology (RSM) by SYSTAT-12. The predicted optimized values were obtained as 6.247 (pH), 0.268 mg/L (iron sulphate), and 0.439 mg/L (nickel concentration) with maximum cumulative biohydrogen production 3.2 L H2/L from statistical analysis. Experimental validation of the optimized setpoints produced maximum cumulative hydrogen production of 2.77 L/L medium (highly close to the predicted response i.e. 3.2 L H2/L) with a maximum yield of 3.85 mol H2/mol sugar. At the predicted optimized condition, a batch test was performed using rice water as substrate which produced maximum output 3.2 mol H2/ mol sugar.

Green-synthesized nickel oxide nanoparticles enhances biohydrogen production of Klebsiella sp. WL1316 using lignocellulosic hydrolysate and its regulatory mechanism

Green synthesis of nickel oxide nanoparticle (NiO-NP) from Eichhornia crassipes (Ec) extract was novelly conducted, and regulatory effect of this NP on fermentative hydrogen production was evaluated. Characterization of the Ec-NiO-NP revealed their cubic and spherical shape, small diameter (9.1 ± 2.6 nm) and high purity. The maximum cumulative hydrogen production and hydrogen yield Y(H2/S) reached 4842.19 ± 23.43 mL/L and 101.45 ± 3.32 mL/gsubstrate, respectively, in the presence of 20 mg/L Ec-NiO-NP, which were 47.29% and 37.78% higher than the control without NPs addition. Evaluation of glucose and xylose utilization efficiency as well as key node metabolites further established the potential of Ec-NiO-NP to improve the reducing sugar conversion and metabolic flux distribution in hydrogen synthesis pathway. Furthermore, addition of 20 mg/L Ec-NiO-NP resulted in enhanced hydrogenase activity with a maximum increase of 623% comparing to the control, and led to changes in the gene expression of both hydrogenase and formate-hydrogen lyase, which play important roles in promoting hydrogen production at different stages of fermentation. This study demonstrates that supplementation with green-synthesized Ec-NiO-NP effectively improves fermentative hydrogen production and regulates key node metabolites alteration and functional gene expression.

Co-production of hydrogen and ethanol by Thermoanaerobacterium thermosaccharolyticum KKU-ED1 from alpha-cellulose and cellulose fraction of sugarcane bagasse

This research aims to evaluate the co-production of hydrogen and ethanol from lignocellulosic materials by Thermoanaerobacterium thermosaccharolyticum KKU-ED1. The optimum conditions for co-production of hydrogen and ethanol in batch fermentation was determined using alpha-cellulose as a basic model substrate to mimic the natural cellulose part of a lignocellulosic material. The optimal conditions attained were an initial pH of 7.0, a temperature of 55 °C, and a cellulose content of 20 g/L, which resulted in the maximum hydrogen production and ethanol (EtOH) yield of 6113 mL H2/L and 1.71 mmol EtOH/g-celluloseconsumed, respectively. The potential of the KKU-ED1 strain to produce hydrogen and ethanol from natural cellulose in sugarcane bagasse was further evaluated under the optimum conditions. Hydrogen production and ethanol yield of 218 mL H2/L, and 0.26 mmol EtOH/g-celluloseconsumed were obtained. Results indicated that the strain KKU-ED1 is a thermophilic cellulolytic bacterium capable of co-producing hydrogen and ethanol from lignocellulosic materials.

Hybrid composite of modified commercial activated carbon and Zn-Ni hydrotalcite for fermentative hydrogen production

Commercial activated carbon (CAC) was modified by a chemical activation agent, H3PO4 with the temperature ranging from 400 to 700 °C (400 °C, 500 °C, 600 °C and 700 °C) for 1 h under N2 atmosphere. The modified commercial activated carbon (mCAC) samples were characterized for surface area, morphology, structure and functional groups to understand the roles of the modified activated carbon in fermentation. All samples (CAC and mCAC) were employed at a concentration of 8.33 g/L. The possible enhancement of hydrogen production via dark fermentation was investigated using sucrose as the substrate. The best catalytic performance was observed at an activation temperature of 600 °C (mCAC600) with hydrogen production of 2.62 mol H2/mol sucrose. This was 17 % higher than the control. The mCAC600 was then used as a supporting material for Zn-Ni-HT (Zn-Ni-HT/mCAC600). The Zn-Ni-HT/mCAC600 was obtained by the incipient impregnation method. The maximum hydrogen production yield was found at 2.95 mol H2/mol sucrose, which is 30 % higher than the control. The Zn-Ni-HT/mCAC600 acted as an alkaline reagent to encounter fatty acid, thereby preventing a pH drop during the fermentation process. Moreover, the supported activated carbon can also adsorb unfavorable VFAs in the system. The release of metal ions from the structure of Zn-Ni-HT/mCAC600 was lower than that of Zn-Ni-HT/CAC, especially for Mg2+ and Al3+. The released ions also helped to enhance the hydrogen production yield, particularly for Ni2+. The Zn-Ni-HT/mCAC600 composite created hybrid functions to promote fermentative hydrogen production.

Application of response surface methodology and dynamic Monte Carlo simulation to study the hydrogen production from formic acid on Ni(1 0 0)

In this research, the maximum yield of hydrogen production from formic acid on Ni(100) has been obtained using the response surface methodology (RSM) and dynamic Monte Carlo simulation (DMC). The RSM was utilized to evaluate the provision parameters in formic acid decomposition. The results of simulation were examined using RSM to optimize the hydrogen production by formic acid on Ni(100). Temperature, formic acid pressure and time of reaction as the effective variables were optimized to obtain the maximum yield of H2 production. The optimum conditions were estimated as temperature 140.17 °C, pressure 2.5 × 10−4 Pa and time of reaction 5.64 s. Using RSM and DMC simulation together, the yield of reaction was improved to a high value 80.25%.

Performance of nickel-iron foam (Ni-Fe) cathode in bio-electrochemical system for hydrogen production from effluent of glucose fermentation

The high cost of Pt-based cathode, and its possibility of being poisoned by the presence of buffer in the electrolyte are two paramount issues in the BES system. The Ni-Fe has become one of the good alternatives because it has excellent catalytic properties, inexpensive, commercially available and low toxicity to microorganisms. In this study, Ni-Fe foam applied as a cathode in dual-chamber BES, while effluent of glucose fermentation as a substrate in the anode side. The characteristic of Ni-Fe surface was analyzed by using field emission scanning electron microscopy. Whereas, the catalytic property of Ni-Fe was evaluated by using linear sweep voltammetry test. The maximum hydrogen production rate and yield obtained were 500 ± 80 m3/m3/d and 470.2 ± 11.2 mL/g COD, respectively. The results show that the Ni-Fe has comparable performance to GF/Pt. Hence it could be used as an alternative cathode in BES application.

Hydrogen Production via Synthetic Biogas Reforming in Atmospheric-Pressure Microwave (915\xa0MHz) Plasma at High Gas-Flow Output

This paper is a contribution to the development of microwave plasma-based technology for hydrogen (H2) production from a so-called synthetic biogas, considered as a mixture of methane (CH4) and carbon dioxide (CO2). The efficiency of hydrogen production via reforming of CH4 in the synthetic biogas flowing through a waveguide-supplied metal cylinder-based microwave plasma source (MPS) operating at atmospheric pressure was tested experimentally. The MPS operated at a frequency of 915 MHz. The working plasma-forming gas was a mixture of CH4:CO2 of volume ratios from 0 to 1. Its flow rate was varied from 3 to 12 m3/h. The microwave power absorbed by the plasma was up to 7.5 kW. The experiment showed that using this kind of MPS, the plasma processing of the synthetic biogas can be run stably at high flow rates (up to 12 m3/h). The optimal CH4:CO2 ratio in terms of high energy efficiency of the microwave plasma reforming of CH4 was found to be 40:60. The maximum achieved hydrogen production rate was 156 g(H2)/h at a microwave absorbed power of 7.5 kW (at a flow rate of 6 m3/h) with the energy efficiency of hydrogen production of 21 g(H2)/kWh. The maximum energy yield of hydrogen production of 24 g(H2)/kWh was achieved at 4.5 kW of the microwave absorbed power (the hydrogen production rate was 108 g(H2)/h in this condition). The maximum methane conversion degree and maximum hydrogen selectivity were 86.5% and 73.3%, respectively at an absorbed microwave power of 6.5 kW (at 3 m3/h).

Effect of triclocarban on hydrogen production from dark fermentation of waste activated sludge

This work aims to investigate whether and how TCC affects hydrogen production using both experimental and model approaches. Experimental results showed that the exposure of TCC not only enhanced the hydrogen production yield but also promoted the hydrogen yield potential and hydrogen production rate. The maximum hydrogen production yield and hydrogen production rate increased from 10.1 ± 0.2 to 14.2 ± 0.2 mL/g VSS and 0.09 to 0.13 mL/g VSS·h, respectively, when TCC level increased from 0 to 1403 ± 150 mg/kg TSS. Mechanism exploration showed that the presence of TCC significantly promoted the release of substances and observably facilitated the acidification process but seriously inhibited the methonogenesis and homoacetogenesis processes. Further investigations with enzyme analysis revealed that TCC importantly increased the activities of acetate kinase and [FeFe] hydrogenase but seriously inhibited the activities of carbon monoxide dehydrogenase and Coenzyme F420.

Improvement of photofermentative biohydrogen production using pre-treated brewery wastewater with banana peels waste

In this study, the impacts of banana peels pre-treatment stage on photofermentative hydrogen production of Rhodobacter sphaeroides 158 DSM using brewery wastewater (BWW) were investigated in a batch bioreactor. The experimental results indicate that banana peels pre-treatments can significantly enhance the cumulative hydrogen production. The maximum hydrogen production yield (408.33 mL H2 L−1wastewater) was achieved from the substrate, which was composed of 50% BWW pretreated with 1 g L−1 of banana peels for 2 h and 50% standard medium. This highest amount of hydrogen production was 2.7-folds higher than those that applied the same percentage of raw BWW as the substrate source.

Experimental continuous sludge microwave system to enhance dehydration ability and hydrogen production from anaerobic digestion of sludge

Dehydrating large amounts of sludge produced by sewage treatment plants is difficult. Microwave pretreatment can effectively and significantly improve the dewaterability and hydrogen production of sludge subjected to anaerobic digestion. The aim of this study was to investigate the effects of different microwave conditions on hydrogen production from anaerobic digestion and dewaterability of sludge. Based on an analysis of the electric field distribution, a spiral reactor was designed and a continuous microwave system was built to conduct intermittent and continuous experiments under different conditions. Settling Volume, Capillary Suction Time, particle size, and moisture content of the sludge were measured. The results show that sludge pretreatment in continuous experiments has equally remarkable dehydration performance as in intermittent experiments; the minimum moisture content was 77.29% in the intermittent experiment under a microwave power of 300W and an exposure time of 60sec, and that in the continuous experiment was 77.56% under a microwave power of 400W and an exposure time of 60sec. The peak measured by Differential Scanning Calorimeter appeared earliest under a microwave power of 600W and an exposure time of 180sec. The heat flux at the peak was 4.343W/g, which is relatively small. This indicates that microwave pretreatment induced desirable effects. The maximum yield of hydrogen production was 7.967% under the conditions of microwave power of 500W, exposure time of 120sec, and water bath at 55°C. This research provides a theoretical and experimental basis for the development of a continuous microwave sludge-conditioning system.

Dark fermentative hydrogen production from sucrose and molasses

Summary There are many factors affecting the dark fermentative hydrogen production. The interaction of these factors, that is, their combined effects, should be investigated for better design of the systems with stable and higher hydrogen yields. This study aimed to investigate the combined effects of initial substrate, pH, and biomass (or initial substrate to biomass) values on hydrogen production from sucrose and sugar-beet molasses. Therefore, optimum initial chemical oxygen demand (COD), pH, and volatile suspended solids (VSS) or initial substrate to biomass (VSS) ratio (S/Xo) values leading to the highest dark fermentative hydrogen production were investigated in batch reactors. An experimental design approach (response surface methodology) was used. Results revealed that when sucrose was the substrate, maximum hydrogen production yield (HY) of 2.3 mol H2/mol sucroseadded was obtained at initial pH of 7 and COD of 10 g/L. Initial S/Xo values studied (4–20 g COD/g VSS) had no effect on HY, while the initial pH was found as the parameter mostly affecting both HY and hydrogen production rate (HPR). When substrate was molasses, initial COD concentration was the only variable affecting HY and HPR. Maximum of both was achieved at 10 g/L initial COD. Initial VSS values studied (2.5–7.5 g/L) had no effect on HPR and HY. This study also indicated that molasses leads to homoacetogenesis for potentially containing intrinsic microorganism and/or natural constituents; thus, sucrose is more advantageous for hydrogen production via fermentation. Homoacetogenesis should be prevented for effective optimization via response surface methodology, if substrate is a natural carbon source potential to have intrinsic microorganisms. Copyright © 2017 John Wiley & Sons, Ltd.

Characterization and hydrogen production performance of a novel strain Enterococcus faecium INET2 isolated from gamma irradiated sludge

A novel hydrogen-producing strain was isolated from the gamma irradiated sludge and identified as Enterococcus faecium INET2 by 16S rRNA gene analysis. The hydrogen production performance by E. faecium INET2 was investigated at temperature of 25–40 °C, initial pH of 5–10, substrate concentration of 5–20 g/L glucose and inoculation ratio of 5–30%. The suitable condition for hydrogen production was determined to be 35 °C, initial pH 7, 15 g/L glucose and 10% inoculation ratio. E. faecium INET2 was immobilized using polyvinyl alcohol (PVA)-sodium alginate and applied for hydrogen production. The maximum cumulative hydrogen production and hydrogen yield were 130 mL H2/100 mL, 1.16 mol H2/mol glucose for free cells, and 202 mL/100 mL, 1.69 mol H2/mol glucose for the immobilized cells. Acetic acid and butyric acid were the major volatile fatty acids formed during the fermentation process, and the process was dominated by acetate-type fermentation. These results indicate that E. faecium INET2 is a promising candidate for fermentative hydrogen production.

Best mode for photo-fermentation hydrogen production: The semi-continuous operation

In this study, a semi-continuous culture mode was used for photo-hydrogen production by Rhodopseudomonas sp. nov. strain A7 and 3 key operating parameters (the interval feeding time, initial feeding time and the feeding volume ratio) were optimized to improve hydrogen production performance. The rate and yield of hydrogen production decreased from 19.7 ml-H2/l/h to 4.63 ml-H2/l/h with the interval feeding time increased from 1 day to 3 days, and the yield of hydrogen decreased gradually and reached the maximum value of 2.11 mol-H2/mol acetate when the interval feeding time is at 1 day. The initial feeding time was extended from 3 days to 4 days, the rate of hydrogen production decreased from 24.8 ml-H2/l/h to 23 ml-H2/l/h, and the rate of hydrogen production decreased to 22.2 ml-H2/l/h when it was extended to 5 days. And specific yield of hydrogen production of 2.65, 2.48 and 2.38 mol-H2/mol-acetate was obtained, respectively. The yield of hydrogen increased with the increase of feeding volume ratio from 10% to 40% and reached a maximum value of 3.22 mol-H2/mol acetate at feeding volume ratio of 40%, the specific yield and rate of hydrogen production gradually decreased with the feeding volume ratio further increased to 60%. The optimal parameters of semi-continuous operation are as following: the initial feeding time of 3 days, interval feeding time of 1 day and feeding volume ratio of 40%. In these conditions, the maximum yield (3.22 mol-H2/mol acetate) and rate (30 ml-H2/l/h) of hydrogen production and light energy conversion efficiency of 1.9% were obtained. Compared to other hydrogen production mode (batch, continuous and fed-batch culture), the semi-continuous culture mode for photo-hydrogen production exhibited great potential due to following advantages: less loss of biomass, the well stability of system, easy operation and control. Therefore it is the best operation mode for photo-hydrogen production with high yield of hydrogen production and light energy conversion efficiency.

Bio-hydrogen production from palm oil mill effluent (POME): A preliminary study

Raw palm oil mill effluent (POME) from a cooling pond and sludge from anaerobic pond of the POME treatment plant at Labu palm oil mill were collected for the study. The treatment of POME was carried out under anaerobic fermentation process, with an objective to produce bio-hydrogen via microflora. The experiments were conducted in 500 mL bioreactor under mesophilic operation at 37 °C with different pH (4.5, 5.0, 5.5, and 6.0) and sludge percentage values (2.5, 5, 7.5, and 10% (w/v)). The source of inoculum was used in POME sludge as hydrogen producing bacteria. From batch experiments, the maximum hydrogen production yield obtained was 5.988 ± 0.5 L H2/L-med at 10% POME sludge (w/v) with an optimum pH of 5.5 and mesophilic temperature of 37 °C. Methane free biogas consist of 36% maximum hydrogen and 64% carbon dioxide was produced during the process.

Performance evaluation of sorption enhanced chemical-looping reforming for hydrogen production from biomass with modification of catalyst and sorbent regeneration

Process simulation of sorption enhanced chemical-looping reforming for hydrogen production from biomass was investigated. Corn stover was converted to bio-oil via pyrolysis prior to sorption enhanced chemical-looping reforming (SE-CLR). NiO was used as a catalyst and oxidizing agent and CaO was used as a CO2 sorbent which are cycled between the reduction and oxidation reactors. Modification of the process to incorporate a step for catalyst and sorbent regeneration was examined and compared with conventional sorption enhanced chemical-looping reforming process. By modifying the SE-CLR process with the recirculating of solids from the air reactor directly to the reformer, a maximum bio-oil conversion rate of 92%, a maximum hydrogen production yield of 153.4gH2/kg corn stover, and a maximum hydrogen purity of 77% v/v can be obtained with a circulated NiO to bio-oil molar ratio (CNB) of 12.3; a circulated CaO to bio-oil molar ratio (CCB) of 125.2; and where the ratio of solids recovered by the air reactor from the calcination reactor (α) was set as 1, and the ratio of solids flowing directly from the air reactor to the reformer (β) was set as 0.02. The split of a fraction of solids streams to feed directly back to the reformer offers a great impact process control as operating conditions can be broadened.

Investigating the effects of iron and nickel nanoparticles on dark hydrogen fermentation from starch using central composite design

The effects of Fe0 and Ni0 nanoparticles on mesophilic dark hydrogen fermentation from starch were investigated using heat-shock pretreated anaerobic sludge in batch reactors. Starch concentration in the range of 0–20 g/L was used in the presence of 0–50 mg/L of each Fe0 and Ni0 nanoparticles while the initial pH of all experiments was adjusted to 7. The hydrogen production was optimized using response surface methodology (RSM) in a central composite design (CCD) mode. The results showed the significance of the linear effect of starch and Fe0 concentrations, the interactive effect between Fe0 and Ni0 concentrations, and the squared effect of starch concentration on the biohydrogen production. The maximum yield of hydrogen production 149.8 mL/g-VS was obtained at starch, Fe0 and Ni0 concentrations of 5.37 g/L, 37.5 mg/L, and 37.5 mg/L, respectively. This was nearly 200% higher than those in the corresponding control test. Moreover, the analysis of metabolites indicated the hydrogen production through acetic acid pathway.

Effect of organic loading rate on hydrogen production from sugarcane vinasse in thermophilic acidogenic packed bed reactors

This study evaluated the effect of organic loading rate (OLR) on hydrogen production in up-flow anaerobic packed bed reactors (APBR) continuously fed with sugarcane vinasse. Four thermophilic up-flow APBR were operated in parallel at different ORL. Continuous hydrogen production was detected. The optimum OLR of 84.2 kg-COD m−3 d−1 was assessed by polynomial adjustment, which predicted a maximum Volumetric Hydrogen Production (VHP) and hydrogen yield (YH2) of 1117.2 mL-H2 d−1 L−1reactor and 2.4 mol-H2 mol−1total carbohydrates, respectively. The microbial composition was monitored using 16S rRNA gene by Terminal Restriction Fragment Length Polymorphism (T-RFLP) analysis and quantification of Fe-hydrogenase gene by real-time PCR which was affected by the OLR. The number of the Fe-hydrogenase genes was proportional to the monitored hydrogen production and yield. Hydrogen-producing strains were isolated, and the 16S rRNA gene sequences were highly homologous to those of Thermoanaerobacterium thermosaccarolyticum. The ability of vinasse as substrate for hydrogen production was confirmed for both strains.