Photofermentative Hydrogen Production Research Articles

Photohydrogen production from lactose and lactate by recombinant strains of Rhodobacter capsulatus: Modeling and optimization

Photofermentative hydrogen production from synthetic mixtures of lactose and lactate mimicking cheese whey was modeled and optimized using Design of Experiments and Response Surface Methodology. Five continuous parameters (light intensity, pH, lactose, lactate and glutamate concentrations) were studied as a function of buffer type (KPi or Borax) using two recombinant bacterial strains. For Rhodobacter capsulatus B10(lacZ), buffer type influenced the optimal parameter values but the optimal responses were similar in both buffers. In contrast, for R. capsulatus IR3(lacZ), responses were higher in Borax buffer than in KPi and were significantly higher than in strain B10(lacZ). Thus, the experimental optimized responses for specific volumetric H2 production, volumetric H2 production rate and substrate (lactose plus lactate) to H2 conversion rate in Borax buffer, were 12,150 ml L−1, 48.5 ml L−1 h−1 and 41.2%, respectively, for IR3(lacZ) compared to 6150 ml L−1, 33.5 ml L−1 h−1 and 32.5%, respectively, for B10(lacZ).

Analysis of shaking effect on photo-fermentative hydrogen production under different concentrations of corn stover powder

High solid phase and easily congeal affect the mass transfer in the photo-fermentative biohydrogen production when taken straw biomass as substrate. Hence, oscillator was adopted to provide the shaking condition to enhance the mass transfer situation in this paper. Diverse shaking velocity (0, 80, 120 and 160 rpm) and substrate concentration (0, 2, 4, 6, 8 and 10 g) were studied, to evaluate the influence on the hydrogen yield capacity. The results showed that shaking could help to accelerate of gas release, shorten the fermentation time, and improve hydrogen production rate. Hydrogen yield was significantly enhanced at high substrate concentration under shaking condition. Highest hydrogen yield of 57.08 ± 0.83, 57.62 ± 1.37, 62.28 ± 0.84 mL/g-volatile solids (VS) were observed at shaking velocities of 80, 120 and 160 rpm with 6, 8 and 10 g corn stover powder, respectively. On the contrary, shaking significantly reduced the potential of hydrogen yield at a low substrate concentration, and the lower hydrogen yield obtained at the higher shaking velocity. As the lowest hydrogen yields of 27.68 ± 1.02 and 41.93 ± 0.40 mL/g VS were obtained at shaking velocity of 160 rpm with 2 and 4 g corn stover powder, respectively.

High NH3[sbnd]N tolerance of a cheR2-deletion Rhodobacter capsulatus mutant for photo-fermentative hydrogen production using cornstalk

A mutant, JL1601, with a cheR2 gene deletion was constructed with Rhodobacter capsulatus JL1 as the wild type strain. The effects of pH, ammonia nitrogen concentration and light intensity on the photo-fermentative hydrogen production performance of JL1601 were studied. Suitable pH range for hydrogen production with the cheR2- mutant migrated from faintly acid to weak alkaline condition, and R.capsulatus JL1601 (cheR2-) showed higher NH3N tolerance. The mutant performed better H2 production performance than the wildtype under the same illumination condition. The maximum H2 yield and rate of R.capsulatus JL1601 (cheR2-) obtained to be 4406.7 ± 45.9 mL/L and 54.1 ± 1.6 mL/(L·h) with the mixture of acetate and butyrate as the carbon sources, which were increased by 36.3% and 12.3% in comparison to those of wildtype, respectively. Practical experiments using acid-enzymatic pretreated cornstalk as the carbon source indicated that, the maximum hydrogen yields by the mutant JL1601 (cheR2-) was up to 224.85 ± 5.18 mL-H2/g-cornstalk, which increased by 171.43% compared with that of wild type strain.

Synergistic effects and optimization of photo-fermentative hydrogen production of Rhodobacter sphaeroides DSM 158

The synergistic effects and optimization of pH, carbon-to-nitrogen ratio (C/N), and light intensity (I) on the photo-fermentative hydrogen production of Rhodobacter sphaeroides 158 DSM and light conversion efficiency have been investigated under different conditions of pH (6.5–8); C/N (15–35); and light intensity (35–185 W m−2). Response surface methodology (RSM) and Box-Behnken experimental design (BBD) were used to identify the optimum values of the three key parameters of pH, C/N, and I, based on the impact on hydrogen production potential (HPP), hydrogen production rate (HPR), and light conversion efficiency η. With desirability value of 0.91, the optimum values of 7.4, 27.5, and 126 W m−2 were identified for pH, C/N, and I respectively, with HPP, HPR and η reaching 960 mL L−1, 41.74 mL L−1 h−1, and 0.31 respectively. Regression analysis indicated a good fit between experimental and model data. The study showed that both C/N ratio and I have crucial and significant effect on the HPP, HPR and η, followed by pH, the synergistic effect of pH–I and C/NI on the light conversion efficiency (η) was significant while pH C/N was insignificant. The results and analysis obtained could be very useful for better optimizing the photo-fermentative hydrogen production.

Effect of humic acid on photofermentative hydrogen production of volatile fatty acids derived from wastewater fermentation

Abstract Humic acid (HA) containing in the inoculated waste activated sludge (WAS) would be released into the fermentation liquid during dark fermentative hydrogen production. Nevertheless, the influence of HA on the photofermentative hydrogen production from volatile fatty acids (VFAs) left in the dark fermentation liquid by photosynthetic bacteria (PSB) had not been investigated. This study measured the effects of sludge humic acid (SHA) and AQS (anthraquinone-2-sulfonic acid, model humic acid) on the photofermentative hydrogen production from VFAs. Results showed that the photofermentative hydrogen production was reduced by 12.0% and 35.4% in synthetic wastewater with 100 mg/L of the added SHA or AQS, respectively. Mechanistic studies showed that high concentrations of SHA and AQS inhibited the activity of nitrogenase and development of PSB biomass, as well as damaging the cell membranes and causing significant death of PSB, leading ultimately to a significant decrease of photofermentative hydrogen production. Moreover, fluorescence spectra showed that SHA had a small molecular weight and a low degree of humification compared to that of AQS, which caused more negatively influence of AQS on photo hydrogen generation from VFAs. Finally, the feasibility of removing SHA from anaerobic dark fermentation liquid of wastewater to improve photofermentative hydrogen production was testified.

Photohydrogen production from dark-fermented palm oil mill effluent (DPOME) and statistical optimization: Renewable substrate for hydrogen

Biological hydrogen production through photo-fermentative process using dark fermented palm oil effluent (DPOME) is a cost effective and environmentally benign process. In this study, effect of various factors like light intensity, agitation rate and dilution of DPOME on the hydrogen productivity of Rhodopseudomanas palustris were investigated using batch system. Investigation methods like response surface methodology (RSM) and Box-Behnken design were employed to investigate the optimum conditions for enhanced photo-fermentative hydrogen production. The regression analysis suggested that hydrogen yield was well fitted by a quadratic polynomial equation (R2 = 0.92). The hydrogen production was investigated by varying the intensity levels of these three independent variables, in which all have significant influences on hydrogen yield. The set of 19 experimental runs were conducted to optimize these variables. The highest hydrogen yield of 3.07 ± 0.66 H2 yield mol-H2/mol-acetate was obtained under the optimum condition of light intensity 250 W/m2, agitation rate 200 rpm, and 30% dilution of DPOME. The experimentally obtained hydrogen yield found out to be in a good agreement with predicted yield which was about 2.80 mol-H2/mol-acetate. In short, results suggest that experimental strategy using RSM approach along with Box-Behnken design can be a promising approach to achieve enhanced biological hydrogen production.

Photofermentative hydrogen production from molasses: Scale-up and outdoor operation at low carbon-to-nitrogen ratio

Photofermentative hydrogen production was carried out under outdoor conditions with a Rhodobacter capsulatus strain on molasses, a renewable and sustainable feedstock. An existing photobioreactor design was scaled-up from 9 L to 20 L. The decreased carbon-to-nitrogen (C/N) ratio of 13.0, compared to our previous work, accelerated growth and resulted in a reduced lag period for hydrogen production as well as higher productivities in the exponential phase. However, the low C/N ratio also promoted a high optical density due to growth, limiting light transmission. Still, the maximum productivity was found as 0.47 mol H2/(m3·h), significantly higher than our result with the smaller reactor volume. High rates of production could not be maintained presumably due to the combined effects of cloudy periods, the aforementioned C/N ratio and decreasing pH. These results suggest that the scale-up was successful and there is potential for further improvement using optimal C/N ratio and cell concentration values.

Sequential dark and photo fermentation hydrogen production from hydrolyzed corn stover: A pilot test using 11 m3 reactor

Pilot tests of sequential dark and photo fermentation H2 production were for the first time conducted in a 11 m3 reactor (3 m3 for dark and 8 m3 for photo compartments). A combined solar and light-emitting diode illumination system and a thermal controlling system was installed and tested. With dark fermentation unit maintained at pH 4.5 and 35 °C and photo fermentation unit at pH 7.0 and 30 °C, the overall biogas production rate using hydrolyzed corn stover as substrate reached 87.8 ± 3.8 m3/d with 68% H2 content, contributed by dark unit at 7.5 m3-H2/m3-d and by photo unit at 4.7 m3/m3-d. Large variation was noted for H2 production rate in different compartments of the tested units, revealing the adverse effects of poor mixing, washout, and other inhomogeneity associated with large reactor operations.

Bio-hydrogen production from waste materials: A review

When hydrogen burns in air, it produces nothing but water vapour. It is therefore the cleanest possible, totally non-polluting fuel. This fact has led some people to propose an energy economy based entirely on hydrogen, in which hydrogen would replace gasoline, oil, natural gas, coal, and nuclear power. Hydrogen is a clean energy source. Therefore, in recent years, demand on hydrogen production has increased considerably. Electrolysis of water, steam reforming of hydrocarbons and auto-thermal processes are well-known methods for hydrogen gas production, but not cost-effective due to high energy requirements. As compare to chemical methods, biological production of hydrogen gas has significant advantages such as bio-photolysis of water by algae, dark and photo-fermentation of organic materials, usually carbohydrates by bacteria. New approach for bio-hydrogen production is dark and photo-fermentation process but with some major problems like dark and photo-fermentative hydrogen production is the raw material cost. By using suitable bio-process technologies hydrogen can be produced through carbohydrate rich, nitrogen deficient solid wastes such as cellulose and starch containing agricultural and food industry wastes and some food industry wastewaters such as cheese whey, olive mill and baker's yeast industry wastewaters. Utilization of aforementioned wastes for hydrogen production provides inexpensive energy generation with simultaneous waste treatment. This review article summarizes bio-hydrogen production from some waste materials with recent developments and relative advantages.

A comparison between simultaneous saccharification and separate hydrolysis for photofermentative hydrogen production with mixed consortium of photosynthetic bacteria using corn stover

Two different process configurations SSP (simultaneous saccharification photo-fermentation) and SHP (separate hydrolysis photo-fermentation) for photo-fermentative hydrogen production using corn stover by mixed consortium of photosynthetic bacteria were compared. The effects of substrate concentration, initial pH and fermentative temperature on SSP and SHP were investigated. Cell growths and hydrogen production characteristics during the processes of SSP and SHP were also compared. The results showed that the optimal condition of SSP was substrate concentration of 30 g/L, initial pH of 5.5 and fermentative temperature of 40 °C, the corresponding hydrogen production was 83.87 mLH2/g corn stover, which was 27.8% higher than that of SHP. The cell growth time in SSP was longer than that in SHP, especially for extended exponential and stationary stages, which was helpful for hydrogen production. The highest cell concentration in SSP was 3.34 g/L, which was 36.3% higher than that of SHP. The peak hydrogen production rate in SSP increased linearly until 16.33 mL H2/h during 36–120 h, while the peak hydrogen production rate in SHP increased during 12–48 h and then decreased during 48–84 h, with a mean rate of 11.28 mL H2/h.

Scale-up studies for stable, long-term indoor and outdoor production of hydrogen by immobilized Rhodobacter capsulatus

Photofermentative hydrogen production by immobilized Rhodobacter capsulatus YO3 was carried out in a novel photobioreactor in sequential batch mode under indoor and outdoor conditions. Long-term H2 production was realized in a 1.4 L photobioreactor for 64 days using Rhodobacter capsulatus YO3 immobilized with 4% (w/v) agar on 5 mM sucrose and 4 mM glutamate. The highest hydrogen yield (19 mol H2/mol sucrose) and hydrogen productivity (0.73 mmol H2 L−1 h−1) were achieved indoors on 5 mM sucrose. The effect of initial sucrose concentration (5 mM, 10 mM, and 20 mM) on hydrogen production was also investigated. Sustained hydrogen production was carried out under natural, outdoor conditions as well. For the outdoor experiments, the highest hydrogen productivity and yield were obtained as 0.87 ± 0.06 mmol H2 L−1 h−1 and 6.1 ± 0.2 mol H2/mol sucrose, respectively on 10 mM sucrose. Furthermore, this system prevented sudden pH drops and fluctuations caused by the utilization of sucrose throughout the process. These results demonstrate that a proper immobilization setup can lead to long-term efficient and robust hydrogen production even under naturally varying conditions.

Effect of pH on optimization of photofermentative hydrogen production by co-culture of Rhodobacter sphaeroides-NMBL-02 and Bacillus firmus-NMBL-03.

Rhodobacter sphaeroides NMBL-02, photosynthetic purple non sulfur (PNS) bacteria and associated Bacillus firmus NMBL-03 were isolated from water sample collected from 15-20 inches beneath the surface of ponds from Northern region of India in modified Sistrom's media (120 ml) containing 3 g/L malate and 1.2 g/L ammonium sulfate. The isolation was done in air tight serum bottles (120 ml) under tungsten bulb (1.8 kLux light intensity) at 30 oC ± 2 oC. The PNS and heterotrophic bacteria associated with the culture was purified by clonal selection method and characterized by 16S rDNA sequencing. The PNS isolate was identified as Rhodobacter sphaeroides NMBL-02 (ID: 1467407, Accession BANKIT: JN256030) and associated heterotroph as Bacillus firmus NMBL-03 (Gene Bank Accession no.: JN 256029). The effect of initial medium pH on optimization of hydrogen production was investigated in batch process. The maximum hydrogen potential and hydrogen production rate was 2310 ± 55 ml/L and 4.75 ml/L culture/h respectively using glutamate (1.7 mmol/L) as nitrogen source and malate (22.38 mmol/L) as carbon source with 76.39% malate conversion efficiency at initial medium pH 5.0. This co-culture has the ability to produce significant amount of hydrogen in the pH range of 5.0 to 10.0 with 76.39% to 35.71% malate conversion respectively.

Effect of substrate concentration on hydrogen production by photo-fermentation in the pilot-scale baffled bioreactor

Effect of substrate concentration on photo-fermentative hydrogen production was studied with a self-designed 4m3 pilot-scale baffled photo-fermentative hydrogen production reactor (BPHR). The relationships between parameters, such as hydrogen production rate (HPR, mol H2/m3/d), hydrogen concentration, pH value, oxidation–reduction potential, biomass concentration (volatile suspended solids, VSS) and reducing sugar concentration, during the photo-fermentative hydrogen production process were investigated. The highest HPR of 202.64±8.83mol/m3/d was achieved in chamber #3 at a substrate concentration of 20g/L. Hydrogen contents were in the range of 42.19±0.94%–49.71±0.27%. HPR increased when organic loading rate was increased from 3.3 to 20g/L/d, then decreased when organic loading rate was further increased to 25g/L/d. A maximum HPR of 148.65±4.19mol/m3/d was obtained when organic loading rate was maintained at 20g/L/d during continuous bio-hydrogen production.

Photo-fermentative hydrogen production in a 4 m3 baffled reactor: Effects of hydraulic retention time

A 4m3 pilot-scale baffled continuous-flow photoreactor with four sequential chambers (#1–#4) was established and tested to evaluate its photo-fermentative hydrogen production from wastewater that contains (10g/L glucose using a functional consortium at 30°C, under light with an intensity of 3000±200lux with a hydraulic retention time (HRT) of 24–72h. The hydrogen production rate and the broth characteristics varied significantly in the flow direction. The hydrogen production rate was highest in chamber #1, and lower in chambers #2–#4 at an HRT of 72h, while the peak production rate shifted to the latter chambers as the HRT was shortened. The overall H2 production rate increased as HRT decreased, but was not consistent with the predictions that were based on the complete-mixing assumption.

Enhanced photo-fermentative hydrogen production of Rhodopseudomonas sp. nov. strain A7 by biofilm reactor

To achieve stable and efficient photo-fermentative hydrogen production, this work investigated photo-fermentative hydrogen production by forming biofilm on the surface of carrier in the biofilm reactor (BR). Results showed the hydrogen production performance was greatly improved by formed biofilm. The time of hydrogen production and efficiency of substrate utilization were enhanced obviously compared to the control reactor (CR). When the CR was used, hydrogen production stopped at 7th day and maximum cumulative hydrogen volume and hydrogen yield were 1730 ± 87 mL/L and 1.44 ± 0.07 mol H2/mol acetate, respectively. However, in the BR hydrogen production volume of 3028 ± 150 mL/L and hydrogen yield of 2.52 ± 0.13 mol H2/mol acetate were obtained, which were enhanced about 75% compared to that of the CR. The time of hydrogen production extended from 7 days of CR to 12 days of BR and the substrate conversion efficiency increased from 36% of CR to 63% of BR. It was worth noting at 8th day that substrate was almost utilized completely but hydrogen production still lasted for 4 days. This suggested that the formation of biofilm in BR was favorable to continuous hydrogen production and substrate utilization with high efficiency. Results demonstrated the BR can get a more stable and consistent operating process and it was a proper and potential way to produce hydrogen by photo-fermentative bacteria (PFB).

Enhanced photo-fermentative hydrogen production of Rhodopseudomonas sp. nov. strain A7 by the addition of TiO2, ZnO and SiC nanoparticles

In order to strengthen photo-fermentative hydrogen production by different photocatalytic nanoparticles, hydrogen production by photo-fermentative bacteria with addition of TiO2, ZnO and SiC nanoparticles in batch culture were investigated in this study. The results indicated that three nanoparticles could improve hydrogen production performance of Rhodopseudomonas sp. nov. strain A7 under respective optimal conditions. The hydrogen yield of 2.81 mol-H2/mol-acetate was obtained when TiO2 nanoparticles with a concentration of 300 mg/L and size of 25 nm. The concentration of ZnO nanoparticles was at 100 mg/L, hydrogen yield reached 2.64 mol-H2/mol-acetate. Compared with TiO2 and ZnO nanoparticles, SiC nanoparticles exhibited greatest potential for enhancing photo-hydrogen production. By addition of nano-SiC with concentration of 200 mg/L which was prepared at temperature of 1500 °C, the maximum hydrogen volume, average hydrogen content and hydrogen yield of strain A7 were achieved at 2272 mL-H2/L-culture, 85.2% and 2.99 mol-H2/mol-acetate, respectively. And hydrogen production was 18.6% higher than that of alone strain A7 without the addition of nanoparticles. Therefore, the addition of SiC nanoparticles is a promising strategy to improve photo-fermentative hydrogen production from wastewater.

Dynamic modeling of temperature change in outdoor operated tubular photobioreactors.

In this study, a one-dimensional transient model was developed to analyze the temperature variation of tubular photobioreactors operated outdoors and the validity of the model was tested by comparing the predictions of the model with the experimental data. The model included the effects of convection and radiative heat exchange on the reactor temperature throughout the day. The temperatures in the reactors increased with increasing solar radiation and air temperatures, and the predicted reactor temperatures corresponded well to the measured experimental values. The heat transferred to the reactor was mainly through radiation: the radiative heat absorbed by the reactor medium, ground radiation, air radiation, and solar (direct and diffuse) radiation, while heat loss was mainly through the heat transfer to the cooling water and forced convection. The amount of heat transferred by reflected radiation and metabolic activities of the bacteria and pump work was negligible. Counter-current cooling was more effective in controlling reactor temperature than co-current cooling. The model developed identifies major heat transfer mechanisms in outdoor operated tubular photobioreactors, and accurately predicts temperature changes in these systems. This is useful in determining cooling duty under transient conditions and scaling up photobioreactors. The photobioreactor design and the thermal modeling were carried out and experimental results obtained for the case study of photofermentative hydrogen production by Rhodobacter capsulatus, but the approach is applicable to photobiological systems that are to be operated under outdoor conditions with significant cooling demands.

Overexpressing atpXF enhanced photo-fermentative hydrogen production performance of Rhodobacter sphaeroides

The effects of overexpressing atpXF genes encoding b2 subunits of F0F1-ATPase in Rhodobacter sphaeroides HY01 on ATPase, nitrogenase and photo-fermentative hydrogen production activities were studied. The results showed that the expression levels of atpXF and f1 operon in ZTHBB (F0P+atpXF+) enhanced by 1870% and 40% while its expression levels of f0 operon and nif decreased by 20% and 50% compared with those of ZTH, respectively; and the expression levels of b2 subunits, f0 operon, f1 operon and nif in ZTHCB (pucP+atpXF+) enhanced by 370%, 60%, 130% and 160% compared with those of ZTH, respectively. The ATP contents of ZTHBB and ZTHCB increased by 41.5% and 52.8% compared with that of ZTH, and their nitrogenase activities were increased by 30.0% and 41.0% compared with that of ZTH, respectively. When 25 mM acetic acid and 34 mM butyric acid were employed as carbon source and 6 mM l-glutamate was employed as nitrogen source, their hydrogen yields were 7677 ± 176 mL/L (ZTHBB) and 8458 ± 129 mL/L (ZTHCB), which increased by 16.0% and 29.1% compared with that of ZTH, and their maximum hydrogen production rates were 98.0 ± 4.3 mL/(L·h) (ZTHBB) and 100.1 ± 5.1 mL/(L·h) (ZTHCB) under the same conditions, which increased by 14.6% and 17.1% compared with that of ZTH, respectively. The results suggest that overexpressing atpXF could enhance the expression level of F0F1-ATPase and hydrogen production performance of purple non-sulfur bacteria.

The hydrogen production characteristics of mixed photoheterotrophic culture

Photofermentative hydrogen production from glucose was investigated using the mixed photoheterotrophic culture (NG07). High-throughput sequencing was applied to describe the characteristics of the diversity of the microbial community. Bioinformatic analysis of the sequencing result showed that photosynthetic bacteria were dominant in the microbial populations. Several key parameters were investigated by NG07 to assess biohydrogen production. Under optimal condition with 70 mM glucose, 5.0 mg/L Fe2+, and 35 °C temperature, a high hydrogen production rate (HPR) was 136.0 ± 5.6 mL/L/h, which is higher than previous reports. That was the first time the study had found the mixed microbial community could resist the high temperature of 45 °C for photohydrogen generation, and increasing glucose concentration would result in higher hydrogen yield. These results implied that the mixed photoheterotrophic culture had a high temperature tolerance and the possibility of bio-hydrogen production in high temperature region.

Photofermentative production of hydrogen and poly-β-hydroxybutyrate from dark fermentation products

The aim of this work is to investigate the hydrogen and poly-β-hydroxybutyrate (PHB) production during the photofermentative treatment of the effluent from a dark fermentation reactor fed with the organic fraction of municipal solid waste. Two different inocula, an adapted culture of Rhodobacter sphaeroides AV1b and a mixed consortium of purple non sulphur bacteria have been investigated under the same operational conditions. Different hydrogen productivities of 364 and 559NmL H2 L−1 were observed for the Rhodobacter sphaeroides and the mixed culture consortium tests, respectively: the consortium of PNSB resulted 1.5-fold more productive than the pure culture. On the other hand, Rhodobacter sphaeroides culture showed a higher PHB productivity (155mg PHB g COD−1) than the mixed culture (55mg PHB g COD−1). In all the tests, the concomitant H2 and PHB production was associated to a dissolved COD removal higher than 80%.