Photofermentative Hydrogen Production Research Articles

Furfural Influences Hydrogen Evolution and Energy Conversion in Photo-Fermentation by Rhodobacter capsulatus

Furfural, as a typical byproduct produced during the hydrolysis of lignocellulose biomass, is harmful to the photo fermentation hydrogen production. In this work, the effects of furfural on the photo fermentation hydrogen production by Rhodobacter capsulatus using glucose as substrate were investigated. The characteristics of cell growth, hydrogen production, and fermentation end-products with the addition of different concentrations of furfural (0–20 mM) were studied. The results showed that furfural negatively affected the maximum hydrogen production rate and total hydrogen yield. The maximum hydrogen yield of 2.59 ± 0.13 mol-H2/mol-glucose was obtained without furfural. However, 5 mM furfural showed a 40% increase in cell concentration. Furfural in high concentrations can favor the overproduction and accumulation of inhibitive end-products. Further analysis of energy conversion efficiency showed that most of the energy in the substrate was underused and unconverted when the furfural concentration was high. The maximum glucose consumption (93%) was achieved without furfural, while it dramatically declined to 7% with 20 mM furfural addition. The index of half-maximal inhibitory concentration was calculated as 13.40 mM. Moreover, the possible metabolic pathway of furfural and glucose was discussed.

Photo-fermentative hydrogen production from cheese whey: Engineering of a mixed culture process in a semi-continuous, tubular photo-bioreactor

This work approaches the engineering of photo fermentative hydrogen production from cheese whey, for the scale-up of photo-bioreactors. Firstly, a brief review has been performed to identify the optimal reactor configuration as well as the main literature lacks. Results of the review analysis suggest that tubular photobioreactors are effective for the photo fermentation process. On the other hand, one of the main drawbacks to the scale-up of the proposed systems is the wide use of pure cultures, which requires aseptic environments and carefully controlled conditions. Based on the critical evaluation of the state of the art, a semi-continuous tubular photobioreactor, performing mixed culture hydrogen production from cheese whey, under unsterile conditions, was started up. Due to the lack of studies in this field, the case study was developed to provide a methodology for the reactor start-up, which represents the most critical phase of its operation. Preliminary tests were performed to choose the optimal operating conditions. To assess the effectiveness of cheese whey, results were compared to those obtained from a glucose based synthetic substrate, under steady state conditions. Experimental outcomes showed that the optimal Hydraulic Retention Time was 2 days and the most appropriate recirculation/pumping system consisted of an intermittent peristaltic pump. The semi-continuous feeding of cheese whey resulted in 87 mL/L d of hydrogen, which was similar to the productivity obtained under glucose feeding. The characterization of the residual organic content further indicated the possible accumulation of polyhydroxyalcanohates, which was estimated to constitute about the 40% of the total residual COD. These results further addressed the identification of key points to be better investigated to promote the effective photo fermentation scale-up for cheese whey valorization, such as the enhancement of the illumination conditions as well as the search for strategies to improve the uniform exposure of microbial cells to light.

Design, modelling and simulation of a thermosiphon photobioreactor for photofermentative hydrogen production

Currently, most photobioreactors have been designed for cyanobacteria and green algae with comparatively few designed for photofermentative hydrogen production by purple non-sulphur bacteria. Photofermentation experiments are time-consuming and expensive, driving the development of alternative methods for the design of photobioreactors. In this study, computational fluid dynamics (CFD) was used (ANSYS® software package, 2019 R) to design two new thermosiphon photobioreactor (TPBR) configurations for the application of photofermentative hydrogen production by Rhodopseudomonas palustris. The TPBR designs (tubular loop and flat-plate) were simulated and evaluated based on temperature profiles, fluid flow and radiation distribution. Under constant illumination, both reactor designs displayed simulated temperatures suitable for R. palustris as well as achieved fluid velocities exceeding the settling velocity of R. palustris cells; however, both these designs also displayed significant light attenuation. The CFD simulation results were verified by experimental measurements of temperature (< 2.5% error) and fluid velocity (47% error) in a prototype TPBR. Collectively, both the proposed TPBR designs were found to be suitable for photofermentative hydrogen production by R. palustris, with the tubular loop design slightly outperforming the flat-plate in terms of fluid velocity. Furthermore, the proposed CFD method was found to be suitable for the design of photobioreactors, with simulated results closely mimicking their experimentally measured counterparts.

A Thermosiphon Photobioreactor for Photofermentative Hydrogen Production by Rhodopseudomonas palustris.

A thermosiphon photobioreactor (TPBR) can potentially be used for biohydrogen production, circumventing the requirement for external mixing energy inputs. In this study, a TPBR is evaluated for photofermentative hydrogen production by Rhodopseudomonas palustris (R. palustris). Experiments were conducted in a TPBR, and response surface methodology (RSM), varying biomass concentration, and light intensity and temperature were employed to determine the operating conditions for the enhancement of both hydrogen production as well as biomass suspension. Biomass concentration was found to have had the most pronounced effect on both hydrogen production as well as biomass suspension. RSM models predicted maximum specific hydrogen production rates of 0.17 mol m−3h−1 and 0.21 mmol gCDW−1h−1 at R. palustris concentrations of 1.21 and 0.4 g L−1, respectively. The experimentally measured hydrogen yield was in the range of 45 to 77% (±3.8%), and the glycerol consumption was 8 to 19% (±0.48). At a biomass concentration of 0.40 g L−1, the highest percentage of biomass (72.3%), was predicted to remain in suspension in the TPBR. Collectively, the proposed novel photobioreactor was shown to produce hydrogen as well as passively circulate biomass.

Photo-fermentative hydrogen production from organic acids mixtures evaluated through predictive models for Rhodobacter capsulatus strains

This research aimed to evaluate growth and hydrogen production from Rhodobacter capsulatus DSM155 and B10 strains in function of volatile fatty acids (VFA) media composition, as well as to assess the light intensity effect on hydrogen production. The growth of DSM155 and B10 was verified in media containing either acetic acid, butyric acid, or sodium lactate, or a mixture of them (ABL medium), being the ABL medium that produced the maximum cell dry weight, 2.15 and 1.67 g/L for DSM155 and B10, respectively. Biohydrogen production was evaluated in media containing acetic and butyric acids (AB medium), and ABL medium. Both strains presented the highest hydrogen production using ABL medium, being the highest 239.2 mL H2 for DSM155. Finally, light intensity (10, 20, and 30 klux) effect on biohydrogen production was studied using the best strain and medium, i.e., DSM155 and ABL medium. DSM155 produced hydrogen increasingly in the order 10, 20, and 30 klx (2753.5, 2850.5, and 2946.3 mL H2/Lop, respectively); however, the light conversion efficiency into hydrogen showed an inverse trend, 7.47, 4.16, and 2.67 %. In conclusion, R. capsulatus DSM155 is advisable for biohydrogen production using ABL medium in the range 10-30 klux. Moreover, further work is recommended on DSM 155 using organic acid-rich real effluents from dark fermentation.

Photo-fermentative hydrogen production performance of a newly isolated Rubrivivax gelatinosus YP03 strain with acid tolerance

Screening and excavating new photosynthetic bacteria with excellent hydrogen production performance is extremely important for improving the photo-fermentative hydrogen production. A new photosynthetic bacterium YP03 was isolated and identified to be Rubrivivax gelatinosus by morphological characterization and phylogenetic analysis. The effects of several key factors on hydrogen production performance were carried out. The results indicated that YP03 strain showed a preference for the carbon sources, and 5375 ± 398 mL/L of maximum hydrogen yield was obtained using butyrate medium. Meanwhile, YP03 strain could use several nitrogen sources to produce hydrogen, and glutamic acid was the optimum nitrogen source for hydrogen produced. Furthermore, YP03 exhibited better hydrogen production performance at initial pH 7.0, reaction temperature 33 °C and light intensity 5000 lux, and the maximum hydrogen production rate was 108.3 ± 12.4 mL/(Lh), which was relatively high compared with the previous reports by R. gelatinosus. Especially, the proper pH for hydrogen production by YP03 ranged from weak acid to neutral (6.5–7.0) and it still could produce hydrogen at pH 5.5 showing the characteristic of acid tolerance. It suggested that YP03 is a potential candidate for the integration of dark- and photo-fermentative hydrogen production. These findings contribute to our understanding of YP03 strain and provide a prospective photosynthetic bacterium for efficient hydrogen production in future research.

Study on Comparisons of Bio-Hydrogen Yield Potential and Energy Conversion Efficiency between Stem and Leaf of Sweet Potato by Photo-Fermentation

The source of raw materials for hydrogen production can be expanded by using vine waste as a substrate. Likewise, the effectiveness of vine waste can also be improved. However, plant parts such as stems and leaves often differ in physicochemical properties, which significantly affects the effectiveness of biochemical transformation. In this research, sweet potato was used as substrate in photo-fermentative hydrogen production (PFHP) to evaluate differences in bio-hydrogen production yield potential and energy conversion efficiency for its stem and leaf. Physicochemical properties were determined using the following techniques: elementary analysis, SEM, and X-ray diffraction. The Gompertz model was adopted to analyze the kinetic parameters, and energy conversion efficiency was calculated. The results showed that stem samples with loose structures produced more hydrogen, with a total cellulose and hemicellulose content of 44.6%, but crystallinity was only 29.67%. Cumulative bio-hydrogen yield of stem was 66.03 mL/g TS, which was 3.59 times higher than that of leaf. An increase of 258.93% in energy conversion efficiency was obtained when stem was used for PFHP. In conclusion, stem samples were more suitable for PFHP than leaf samples.

Effect of light perturbation on the photo-fermentative hydrogen production of biomass from giant reed

This study aimed to propose a light perturbation strategy to break the balance of the photo-fermentation system, thereby promoting the growth and hydrogen production of photosynthetic bacteria (PSB). This experiment explored the light perturbation of different intensities (4000 Lux, 5000 Lux, 6000 Lux, and 7000 Lux) on the hydrogen production process of giant reed at different times (24 h and 36 h). Under the optimal conditions of 6000 Lux perturbation at 24 h, the cumulative hydrogen yield (HY) and hydrogen production rate (HPR) reached 124.3 mL/g TS and 5.3 mL/g TS/h, which were 19.5% and 26.2% higher than no perturbation, respectively. Moreover, light perturbation at 24 h (1.02 g/L) and 36 h (1.025 g/L) significantly (p < 0.05) increased the dry weight of bacteria, which were 5.5% and 3.9% higher than no perturbation, respectively. In addition, based on matrix scatter analysis, the relationship between the hydrogen production rate after perturbation and the cumulative hydrogen production was the closest. The timing supplemental illumination was a useful approach for enhanced hydrogen yield of photo-fermentation, providing a new way for efficient use of lignocellulosic biomass clean production of hydrogen energy and the industrial promotion of hydrogen production via photo-fermentation.

Towards high light conversion efficiency from photo-fermentative hydrogen production of Arundo donax L. By light–dark duration alternation strategy

Suitable illumination project would help in achieving high light conversion efficiency (LCE) for photo-fermentation. This study proposed an improvement strategy for LCE of photo-fermentative hydrogen production (PFHP) with a photosynthetic consortium by adopting light–dark duration alternation. For this purpose, 6 projects (continues light, 24 h light + 24 h dark, 24 h dark + 24 h light, 48 h light + 48 h light, 48 h dark + 48 h light, and continues dark) light disturbances were carried out to estimate the strategy. The fluctuation of cell growth (OD660) was corresponded to the light–dark alternation. 24 h dark + 24 h light alternation achieved the maximum hydrogen yield (HY) of 390.9 mL/g TS cell (6.7 % higher than continuous light) and maximum improvement of LCE of 114.7%. Moreover, heat map analysis revealed that the light period after inoculation had the closest relation (Pearson’s r = 1) with the average hydrogen production rate (HPR) of photo-fermentation. Besides, decreased dark period after inoculation would increase the hydrogen yield of photo-fermentation.

Comparison of three ionic liquids pretreatment of Arundo donax L. For enhanced photo-fermentative hydrogen production

Ionic liquids (ILs) pretreatment has been regarded as a promising green way to treat lignocellulosic biomass. 1-Butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4), 1-allyl-3-methylimidazolium chloride ([Amim]Cl), and 1-Butyl-3-methylimidazolium Hydrogen Sulfate ([Bmim]HSO4) with different loadings (2, 4, 8, and 16 g/L) were adopted to pretreat the Arundo donax L.. 16 g/L [Bmim]HSO4 pretreated Arundo donax L. obtained the highest sugar yield of 7.9 g/L during the enzymatic hydrolysis and hydrogen yield of 106.1 mL/g TS during the photo-fermentation, which were 68.8 % and 35.3 % higher than those of untreated Arundo donax L., respectively. Moreover, volatile fatty acids (VFAs) distribution revealed that acetic acid was the main by-product during hydrogen production process with ILs pretreated Arundo donax L.. Besides, the relationship between sugar yield and hydrogen yield was the closest based on scatter matrix analysis. This study helps to understand of correlation between ILs pretreatment with the behavior of bioenergy production.

Study of the interrelationship between nano-TiO2 addition and photo-fermentative bio-hydrogen production of corn straw

This study explored the interrelationship between nano-TiO2 addition and photo-fermentative hydrogen production (PFHP) of corn straw. The maximum cumulative hydrogen volume (CHV) was up to 688.8 mL under the optimal photo-fermentative process conditions with nano-TiO2 addition of 300 mg/L. Initial pH and interaction between substrate concentration and light intensity had highly significant effects on PFHP of corn straw with nano-TiO2 addition. With the improvement of CHV, nano-TiO2 addition decreased the optimal initial pH and substrate concentration for PFHP of corn straw. Moreover, nano-TiO2 addition promoted the metabolism of butyric acid and acetic acid by photosynthetic bacteria HAU-M1, and significantly reduced the total concentration of intermediate byproducts during hydrogen production to a low level of 1.6–2.5 g/L, thus making the CHV, maximum hydrogen production rate (HPR) and average hydrogen content (HC) increased by 32.6%, 27.9% and 8.3% respectively over the control without nano-TiO2 addition.

Accelerated start-up for photo-fermentative hydrogen production in biofilm reactor by adding waste effluent

The difficulty and long duration of start-up wastes numerous costs, labors and time and a little fluctuate during the process might fail it. However, studies dealing with the problem hindering accelerated start-up are still insufficient. Current research focused to develop a method for accelerated start-up in an efficient way. This work outlined a novel alternative for accelerated start-up. This joint method, adding waste effluent with applying biofilm reactor, could successfully start up hydrogen production in the first 24 h via increasing ability of hydrogen producers while the control group produced little hydrogen. The two factors, biofilm formation and addition of waste effluent, expressed the combined effects on accelerated start-up. This study suggested that little molecules like quorum sensing system factors and indoles might be the crucial regulating and stimulating factors and express the accelerated start-up ability only in biofilm reactors.

A strategy for successive feedstock reuse to maximize photo-fermentative hydrogen production of Arundo donax L.

This study proposed a strategy to maximize the hydrogen yield by reusing feedstock of Arundo donax L. For this purpose, a successive 4-batch photo-fermentative hydrogen production (PFHP) was carried out to test the strategy. About 50% of total hydrogen yield was additionally obtained by reusing the Arundo donax L for successive 4 times in comparison to single 1st batch (161.4 mL/U. cell dry weight). In addition to the highest hydrogen yield, the maximum hydrogen production rate (6.0 mL/U. cell dry weight /h), and the highest volatile fatty acids (VFAs) concentration (32 mM) were also obtained from the 1st batch, while the 2nd batch gave the maximum substrate conversion efficiency (96.5%). Moreover, a positive relationship between the sum of acetic and butyric acids with hydrogen yields was observed. This strategy would help in enhancing hydrogen yield that coupled with cost reduction for biohydrogen production.

Process optimization and mathematical modelling of photo-fermentative hydrogen production from dark fermentative cheese whey effluent by Rhodobacter sphaeroides O.U.001 in 2-L cylindrical bioreactor

In this study, organic acids present in dark fermentative cheese whey effluent (DFCWE) were utilized to produce biological hydrogen via photo fermentation by R. sphaeroides O.U.001 cells in 2-L double-walled cylindrical PBR with a working volume of 1.5 L. Plackett-Burman design-based analysis revealed organic acid concentration (OA), temperature, and light intensity as the most significant variables. Experiments were performed at different conditions of (OA, 8–16 g L−1), temperature (25–37 °C), and light intensity (8–12 klx). Optimum values were obtained by Box-Behnken design matrix (BBD) based on the impact on hydrogen production rate (HPR) and under optimum values (OA concentration, 12 g L−1; temperature, 31 °C; and light intensity, 10 klx); HPR of 41.94 mL L−1 h−1 was obtained, which lies in close proximity with the predicted production rate of 41.65 mL L−1 h−1 with the correlation coefficient (R2) and coefficient of variance as 0.9801 and 0.0521, respectively. PBR performance for treating DFCWE was checked by performing mathematical modelling using four models. Kinetic study of DFCWE consumption and growth profile of the bacterial cell were investigated by fitting experimental values into Monod and logistic equations, respectively. Parameters of the modified Gompertz equation and Luedeking-Piret models gave proper simulated fitting with experimental H2 production obtained under optimized bioprocess variables. Metabolite analysis revealed that acetic and lactic acids were utilized to produce biohydrogen under uncontrolled pH. Findings of the current investigation could be a promising strategy for obtaining better hydrogen productivity in photo fermentation.

Effect of zinc ion on photo-fermentative hydrogen production performance, kinetics and electronic distribution in biohydrogen production by HAU-M1

The aim of this work was to study the characteristics, kinetics and electronic distribution of photo-fermentation hydrogen production (PFHP) with Zn2+ addition then gave the main results that the addition of Zn2+ can effectively improve hydrogen production with an increasing of 1–5 mg/L Zn2+ concentration. The maximum hydrogen yield of 592 ± 13 mL and shortest lag time of 4.67 h were obtained at 2 mg/L Zn2+. 26.42% of the substrate energy was diverted to H2. Modified Gompertz and Hane-Levenspiel models were applied to evaluate the effect of Zn2+ on PFHP by mixed bacteria HAU-M1, the constants n and m obtained by fitting models were 14.97 and 58.79, respectively, indicating the fermentation system was noncompetitive inhibition, the predicted critical Zn2+ concentration was 40.83 mg/L.

Photo-fermentative hydrogen production by Rhodopseudomonas palustris CGA009 in the presence of inhibitory compounds

This study investigated Rhodopseudomonas palustris CGA009 biohydrogen production from compounds commonly found in lignocellulosic steam explosion hydrolysate, by examining the effect of individual inhibitory phenolic and furan compounds found in hydrolysates, under photo-fermentative anaerobic conditions. Since lignocellulose is often converted into ethanol via yeast-mediated fermentation, the tolerance of R. palustris CGA009 towards ethanol inhibition was also tested at a concentration range of 0.25–14% (v/v) under anaerobic photo-fermentative conditions. Hydrogen production was enhanced by compounds such as syringaldehyde (0.03 g/L), which accumulated total hydrogen of 960 mL over the cultivation period. In contrast, a reduction in hydrogen production of 1.4 fold was observed in vanillin-containing solutions (0.43 g/L), which obtained accumulated total hydrogen of 576 mL. Increasing ethanol concentrations reduced hydrogen production, but cell growth was not affected up to 1% (v/v), a fairly low concentration. R. palustris CGA009 can tolerate comparatively high concentrations of phenolic compounds, suggesting its use for lignocellulose hydrolysate detoxification and hydrogen production.

Effect of chirality of cysteine on the cell growth and photo-fermentative hydrogen production by using acetate as substrate

Cysteine can participate in the essential metabolism of photo-fermentation and plays an important role in biological hydrogen production. However, D-cysteine is usually ignored in current researches despite its potential amounts and unknown effects. This study firstly investigated the photo-fermentative cell growth and hydrogen production with two chiralities of cysteine (L-cysteine and D-cysteine). This and previous studies illustrated proper L-cysteine concentration could improve hydrogen production performance of Rhodopseudomonas sp. nov. strain A7. However, D-cysteine inhibited the cells proliferation and hydrogen production. Groups of initial D-cysteine concentration above 0.3 g/L postponed reactor start-up for several days and obtained little hydrogen production and bacterial biomass. Groups of initial D-cysteine concentration under 0.3 g/L could operate reactor normally in time and obtained about 1000 mL/L hydrogen and 2.0 g/L biomass. Addition time was another key factor, and groups of adding D-cysteine on day 1 influenced little on cells growth but decreased hydrogen production. Other groups with adding time on day 2–5 obtained normal biomass and hydrogen production. Besides, 0.3 g/L functioned as the limit concentration in different initial biomass concentrations for D-cysteine. This work concluded whether the cells could grow and produce hydrogen depended on the addition time and initial D-cysteine concentrations. D-cysteine determined the duration of adapt phase and was regarded as the quorum sensing factor. Furthermore, although biofilm reactors could improve hydrogen production compared to control reactor, biofilm showed little influence on D-cysteine limit concentration. This study would pave the way for the future photo-fermentative hydrogen production.

Integrated pre-treatment stage of biosorbent – sonication for mixed brewery and restaurant effluents to enhance the photo-fermentative hydrogen production

In this study an integrated pre-treatment stage of waste banana peel biosorbent and sonication was investigated to qualify a mixture of brewery (BE) and restaurant (RE) effluents for photo fermentative hydrogen production without using standard medium. Different blending ratios of brewery and restaurant effluents and different sonication amplitudes (30, 60, and 90%) and sonication time (15, 25, 35, and 45 min) were investigated. The experimental results demonstrated that applying the proposed integrated pre-treatment (2 g L−1 waste banana peel biosorbent and 35 min sonication at 60% amplitude) for a mixture of 70% RE and 30% BE enhanced the cumulative biohydrogen production to 110 ± 4 mL (144% enhanced), while applying single pre-treatment stage (2 g L-1 banana peels waste biosorbent) enhanced the cumulative biohydrogen production to 83 mL (84% enhanced). Furthermore, more than 46% of soluble chemical oxygen demand (SCOD) removal was achieved during photo-fermentative hydrogen production process. The results also demonstrated that the proposed integrated pre-treatment stage is a promising technique not only for enhancing the biohydrogen production but also contributes in the treatment of the wastewater by reducing the COD.

Insights into correlation between hydrogen yield improvement and glycerol addition in photo-fermentation of Arundo donax L.

This study aimed to explore the correlation between hydrogen yield improvement of photo-fermentation of Arundo donax L. and glycerol addition. Different glycerol concentrations (g/L) (0, 10, 15, 20, and 30) were replenished to establish co-substrate system. And statistical analysis was introduced to evaluate the correlation. The maximum hydrogen yield improvement (294%) was obtained from glycerol addition of 15 g/L in comparison with mono-substrate system of Arundo donax L. Under the optimal glycerol addition (15 g/L), the glycerol/Arundo donax L. ratio, C/N ratio, initial medium redox potential (Eh), and solid/liquid ratio were 1:1, 25.1, 57 mV, and 1/68, respectively. In addition, canonical correlation analysis (CCA) indicated that initial and final medium redox potential (Eh) had the strongest relationship with yield improvement of photo-fermentation. Moreover, Pearson’s correlation analysis claimed that Arundo donax L./glycerol ratio played a key role during the photo-fermentative hydrogen production (PFHP) process.

Promoting photo-fermentative hydrogen production performance by substituting the rnf promoter in Rhodobacter capsulatus

The Rnf (Rhodobacter nitrogen fixation) complex encoded by rnfABCDGEH genes is a crucial enzyme for the functioning of nitrogenase. In this work, we studied the effect of Rnf complex expression level on hydrogen production in the hydrogen-producing bacterium Rhodobacter capsulatus SB 1003 by expressing rnf genes with three autologous promoters. Substitution of the rnf promoter with that of pucB resulted in a 1.59-fold increase in rnf transcription level and 1.3-fold increase in nitrogenase activity. Under various test conditions, maximum H2 yields and production rates were increased by 12.4%–24.7% and 6.5%–22.9%, respectively. There was a further increase in H2 production when the Prnf::PpucB::rnf fusion construct was expressed in a background strain with both the alternative Fe nitrogenase and the Mo nitrogenase co-expressed. The results demonstrate that the Rnf complex catalyzes a rate-limiting step in photo-fermentative H2 production. The mutants with overexpressed Rnf complex are more competitive than naturally isolated strains under low light condition or in scale-up bioreactors.