Cumulative Hydrogen Yield Research Articles

Enhancement of hydrogen production in dark fermentation of corn stover hydrolysates through composite electric field pretreatment: Improving enzymatic efficiency and regulating microbial metabolic balance

This study investigates the effects of composite electric field pretreatment (CEP) on hydrogen production from corn stover enzymatic hydrolysates in dark fermentation. The findings reveal that under optimal conditions, the CEP group achieved a cumulative hydrogen yield of 77.3 ± 2.6 mL/g TS, marking a 55.3 % increase compared to the control group without the electric field. CEP significantly enhances the fermentation capacity of enzymatic hydrolysates during the acid-stage of dark fermentation by disrupting the lignin structure and optimizing cellulase hydrolysis efficiency. Additionally, pH self-regulation is facilitated through the interaction between volatile fatty acids (VFAs) and ammonia nitrogen. Microbial community analysis revealed that CEP shifts the metabolic balance between Clostridium_sensu_stricto_1 and Lactococcus, leading to increased hydrogen yield and concentration during acid fermentation. Notably, Terrisporobacter exhibited a superior acid-producing capability compared to Bacteroides during the dark fermentation of enzymatic hydrolysates. This study provides a new perspective for the practical application of corn stover.

Advancing two-stage hydrogen production from corn stover via dark fermentation: Contributions of thermally modified maifanite to microbial proliferation and pH self-regulation

This study introduces a two-stage hydrogen production enhancement mechanism using natural particle additives, with a focus on the effects of thermally modified maifanite (TMM) and pH self-regulation on dark fermentation (DF). Initial single-factor experiments identified preliminary parameters for the addition of TMM, which were further optimized using a Box-Behnken design. The established optimal conditions which include mass of 5.5 g, particle size of 120 mesh, and temperature of 324 °C, resulted in a 28.7 % increase in cumulative hydrogen yield (CHY). During the primary hydrogen production stage, TMM significantly boosted the growth and activity of Clostridium_sensu_stricto_1, enhancing hydrogen output. Additionally, a pH self-regulating phenomenon was observed, capable of initiating secondary hydrogen production and further augmenting CHY. These findings presented a novel and efficient approach for optimizing biohydrogen production, offering significant implications for future research and application in sustainable energy technologies.

Enhancement of biohydrogen production by photo-fermentation of corn stover via visible light catalyzed titanium dioxide/activated carbon fiber

In this study, titanium dioxide/activated carbon fiber (TiO2/ACF) was synthesized by liquid-phase deposition method and the effect of TiO2/ACF on the performance of photo-fermentation biohydrogen production (PFHP) from corn stover under visible light catalysis was discussed. Results show the maximum cumulative hydrogen yield (CHY) obtained under the optimal conditions was 74.0 ± 1.3 mL/g TS with TiO2/ACF addition of 100 mg/L, which was twice that without TiO2/ACF addition (36.9 ± 1.0 mL/g TS). Initial pH value had the most significant effect on CHY. The addition of TiO2/ACF promoted the metabolic pathway of nitrogenase to reduce H+ produced by consuming acetic acid and butyric acid to hydrogen, and also shortened the photo-fermentation period. By scanning electron microscopy and X-ray diffraction analysis, the morphology and phase structure of TiO2/ACF after PFHP did not change significantly. This study laid the foundation for the reuse of TiO2 and its practical application in PFHP.

Study on the Effect of Two-Phase Anaerobic Co-Digestion of Rice Straw and Rural Sludge on Hydrogen and Methane Production

Hydrogen and methane, as chemical raw materials with broad application prospects in the future market, can be produced by the two-phase anaerobic co-digestion of rice straw and sludge. The study was carried out using a medium-temperature batch experiment with rice straw, a rural crop residue from Sichuan, and residual sludge from a sewage treatment station. The effect of the mixing ratio of rice straw and rural sludge on hydrogen and methane production from anaerobic digestion was investigated with a view to alleviating the energy crisis and efficient resource utilization. The experimental results showed that hydrogen production was most favorable when rice straw/sludge = 5:1, with a cumulative hydrogen yield as high as 38.59 ± 1.12 mL/g VSadded, while methane production was most favorable when 3:1, with a cumulative methane yield as high as 578.21 ± 29.19 mL/g VSadded. By calculating the energy yield, it was determined that 3:1 is more favorable for the two-phase anaerobic digestion capacity of rice straw and sludge, which is as high as 20.88 ± 1.07 kJ/g VSadded, and its conversion of hydrogen and methane is 0.75% and 78.19%, respectively. The hydrogen production pathway was dominated by the butyric acid type, whose hydrogen production phase pH (5.84 ± 0.13) was slightly higher than the optimal pH for hydrogen-producing bacteria, while the methanogenic phase could meet the optimal pH for methanogenic bacteria (6.93 ± 0.17).

Effect of deep eutectic solvent pretreatment on biohydrogen production from corncob: pretreatment temperature and duration

ABSTRACTDeep eutectic solvent pretreatment with different temperatures and durations was applied to corncob to increase hydrogen yield via photo-fermentation. The correlation of composition, enzymatic hydrolysis, and hydrogen production in pretreated corncobs, as well as energy conversion was evaluated. Deep eutectic solvent pretreatment effectively dissolved lignin, retained cellulose, and enhanced both enzymatic hydrolysis and hydrogen production. The maximum cumulative hydrogen yield obtained under a pretreatment condition of 50°C and 12 h was 677.45 mL; this was 2.72 times higher than that of untreated corncob, and the corresponding lignin removal and enzymatic reduction of sugar concentration were 79.15% and 49.83 g/L, respectively; the highest energy conversion efficiency was 12.08%. The hydrogen production delay period was shortened, and the maximum shortening time was 18.9 h. Moreover, the cellulose content in pretreated corncob was positively correlated with both reducing sugar concentration and hydrogen yield and had the strongest influence on hydrogen production.

Isolation and characterization of Enterococcus faecalis isolate VT-H1: A highly efficient hydrogen-producing bacterium from palm oil mill effluent (POME)

Facultative hydrogen-producing bacteria hold immense potential for fermentative hydrogen and valuable metabolite production. In this study, a mesophilic hydrogen-producing bacterium was isolated from palm oil mill effluent (POME) and identified as Enterococcus faecalis isolate VT-H1 using hybrid sequencing technologies. Our investigation encompassed the growth of the isolate and its capacity for hydrogen and volatile fatty acid (VFA) production. The results revealed that optimal growth occurred when glucose was utilized at 37 °C and initial pH of 7.0, resulting in a final OD600 of 2.58. The isolate demonstrated exceptional hydrogen production capabilities, achieving a maximum cumulative hydrogen yield of 2.22 mol-H2/mol-glucose at 30 °C and pH 7.0, outperforming previously reported E. faecalis strains by 5.84-fold. Kinetic analysis revealed favorable parameters for hydrogen production at 30 °C, with maximum hydrogen production (Hm = 2.63 mol-H2/mol-glucose), maximum hydrogen production rate (Rm = 0.03 mol-H2/mol-glucose·h), and lag-phase time (LPT = 18.34 h). Additionally, E. faecalis isolate VT-H1 exhibited significant butyric acid production (63.0 mM) alongside acetic acid (7.0 mM). Genome analysis unveiled the presence of key enzymes associated with hydrogen production, including formate hydrogen lyase (FHL) complex with formate dehydrogenase subunit alpha (FDH-α), bidirectional [NiFe] hydrogenase, NADH-dependent oxidoreductase subunit E, and NADH-quinone oxidoreductase subunit F. Moreover, genes associated with butyric acid production were also identified. These findings highlight the potential of E. faecalis isolate VT-H1 as a promising candidate for sustainable hydrogen and VFA production. Its unique characteristics, distinct genetic profile, and exceptional hydrogen and VFA production capabilities bring exciting opportunities for future biotechnological applications and further research to optimize and scale-up its potential for industrial use.

Enhancement on photobiological hydrogen production from corn stalk via reducing hydrogen pressure in bioreactors by way of phased decompression schemes

In this project, it was verified that properly reducing the bioreactor hydrogen partial pressure (HPP) could significantly enhance the photo-fermentative hydrogen production (PFHP) by corn stalk. The maximal cumulative hydrogen yield (CHY) of 82.37 mL/g was obtained under full decompression to 0.4 bar, which was 35% higher than that without decompression. To increase CHY and save the pressure control cost, 12-hour, 24-hour and 36-hour decompression schemes were provided, and the optimal decompression phase in fermentation under each scheme was investigated. The 12-hour decompression scheme was suitable for 24–36 h of fermentation; the 24-hour decompression scheme implemented within 12–36 h of fermentation had a more desirable CHY; when adopting the 36-hour decompression scheme, operation during 12–48 h yielded a CHY of 81.70 mL/g that approximated whole process decompression. The strategies of decompression at the appropriate phase of fermentation were innovative, which offered a new option for optimizing PFHP economically.

Optimization and enhancement of biohydrogen production in a single-stage hybrid (dark/photo) fermentation reactor using Fe3O4 and TiO2 nanoparticles

The utilization of nanoparticles to enhance bacterial activity and boost hydrogen production in fermentation processes has gained significant attention due to their unique properties such as high specific surface area and quantum size. This research aimed to improve the biohydrogen yield from food waste by adding iron oxide nanoparticles (Fe3O4) at various concentrations (50, 75, 100, 150, and 200 mg/l) and titanium dioxide (TiO2) at different amounts (25–150 mg/l) to a single-stage hybrid (dark/photo) fermentation reactor. After obtaining the optimal amount of these two nanoparticles, the effect of synergic addition of nanoparticles on hydrogen production yield, was investigated at ratios of Fe3O4/TiO2 = 50/50 and 100/50 mg/mg. At the ratio of Fe3O4/TiO2 = 100/50, the cumulative hydrogen production and yield of hydrogen have increased from 1613 to 3392 ml and 101.60 to 213.66 mlH2/gVS, respectively, compared to the control experiment. We also found that the COD removal rate has enhanced from 28% to 40.1%. In the optimal value, the bacterial growth lag phase has also remarkably decreased from 8.19 to 4.81 h.

Metagenomic Analysis of Bacterial, Archaeal and Fungal Diversity in Two-Stage Anaerobic Biodegradation for Production of Hydrogen and Methane from Corn Steep Liquor.

The main purpose of this study was to identify the microbial communities (bacterial, archaeal and fungal) in a two-stage system of anaerobic bioreactors for the production of hydrogen and methane from the waste substrate-corn steep liquor. Wastes from the food industry are valuable resources with potential in biotechnological production because of their high organic matter contents. In addition, the production of hydrogen and methane, volatile fatty acids, reducing sugars and cellulose content was monitored. Two-stage anaerobic biodegradation processes were performed by microbial populations in the first hydrogen generating bioreactor (working volume of 3 dm3) and in the second methane-generating reactor (working volume of 15 dm3). Cumulative hydrogen yield reached 2000 cm3 or 670 cm3/L a day, while the methane production reached a maximum quantity of 3300 cm3 or 220 cm3/L a day. Microbial consortia in anaerobic digestion systems play an essential role for process optimization and biofuel production enhancement. The obtained results showed the possibility of conducting two separate processes-the hydrogenic (hydrolysis and acidogenesis) and methanogenic (acetogenesis and methanogenesis)-as two stages of anaerobic digestion to favor energy production under controlled conditions with corn steep liquor. The diversity of microorganisms as main participants in the processes in the bioreactors of the two-stage system was followed using metagenome sequencing and bioinformatics analysis. The obtained metagenomic data showed that the most abundant phylum in both bacterial communities was Firmicutes-58.61% and 36.49% in bioreactors 1 and 2, respectively. Phylum Actinobacteria were found in significant quantities (22.91%) in the microbial community in Bioreactor 1, whereas in Bioreactor 2, they were 2.1%. Bacteroidetes are present in both bioreactors. Phylum Euryarchaeota made up 0.4% of the contents in the first bioreactor and 11.4% in the second. As the dominant genera among methanogenic archaea are Methanothrix (8.03%) and Methanosarcina (3.39%), the main fungal representatives were Saccharomyces cerevisiae. New knowledge of anaerobic digestion mediated by novel microbial consortia could be widely used to convert different wastes to green energy.

Enhanced biohydrogen yield and light conversion efficiency during photo-fermentation using immobilized photo-catalytic nano-particles

Bacterial immobilization is a common method in anaerobic fermentation, since of the maintenance of high bacterial activity, insurance of high density microbial during continuous fermentation, and quick adaptability to the environment. While, the bio-hydrogen production capacity of immobilized photosynthetic bacteria (I-PSB) is seriously affected by the low light transfer efficiency. Hence, in this study, photo-catalytic nano-particles (PNPs) was added into the photo-fermentative bio-hydrogen production (PFHP) system, and its enhancement effects of bio-hydrogen production performance were investigated. Results showed that the maximum cumulative hydrogen yield (CHY) of I-PSB with 100 mg/L nano-SnO2 (154.33 ± 7.33 mL) addition was 18.54% and 33.06% higher than those of I-PSB without nano-SnO2 addition and control group (free cells), and the lag time was the shortest indicating a shorter cell arrest time, more cells and faster response. Maximum energy recovery efficiency and light conversion efficiency were also found to be increased by 18.5% and 12.4%, respectively.

Co-production process optimization and carbon footprint analysis of biohydrogen and biofertilizer from corncob by photo-fermentation

In this study, corncob was taken as substrate, the co-production process of biohydrogen and biofertilizer by photo-fermentation was investigated and its carbon footprint analysis was conducted to evaluate the carbon transfer pathway. Biohydrogen was produced by photo-fermentation, and the hydrogen producing residues were immobilized by sodium alginate. Cumulative hydrogen yield (CHY) and nitrogen release ability (NRA) was taken as references, and the effect of substrate particle size on the co-production process was evaluated. Results showed that due to the porous adsorption properties, corncob size of 120 mesh was the optimal one. Under that condition, the highest CHY and NRA were 71.16 mL/g TS and 68.76%, respectively. The carbon footprint analysis indicted that 7.9% carbon element was released as carbon dioxide, 78.3% carbon element was immobilized in the biofertilizer, and 13.8% carbon element was lost. This work is significant of the biomass utilization and clean energy production.

Synergetic effect evaluation of light and mass transfer enhancement strategies on photo fermentative biohydrogen production process: Illumination, shake, and high solid level

During the process of photo fermentative biohydrogen production (PFHP) with high substrate concentration from agricultural waste, the interphase light and mass transfer behavior is hindered, caused by the suspension flow of substrates, resulting in low hydrogen production performance. In the paper, shake and lighting supplied strategy was investigated to soften the restrictions of high substrate concentration of corncob to improve the hydrogen yield and light energy conversion. The response surface methodology (RSM) was adopted to optimize the influence of variables on hydrogen production (substrate concentration, light intensity and shake intensity). Results showed that the maximum hydrogen yield of 48 mL/g TS and the maximum light energy conversion efficiency of 11.04% were obtained at the condition of 150 rpm, 6000 Lux and substrate concentration 55.56 g/L, increased by 603.85% and 598.63% than the static condition, respectively. RSM showed the synergistic effect between variables significantly affected the hydrogen production performance, the optimal enhancement strategies were: shake intensity 153.33 rpm, light intensity 6155.56 Lux and substrate concentration 57.71 g/L. 4.71% error of the predicted cumulative hydrogen yield (490.41 mL) and the actual cumulative hydrogen yield (468.34 mL) indicating the fitting effect of the model was satisfactory.

Optimization of dark fermentative biohydrogen production from rice starch by Enterobacter aerogenes MTCC 2822 and Clostridium acetobutylicum MTCC 11274.

Dark fermentative biohydrogen production (DFBHP) has potential for utilization of rice starch wastewater (RSWW) as substrate. The hydrogen production of Enterobacter aerogenes MTCC 2822 and Clostridium acetobutylicum MTCC 11274, in pure culture and co-culture modes, was evaluated. The experiments were performed in a 2L bioreactor, for a batch time of 120h. The co-culture system resulted in highest cumulative hydrogen (1.13L H2/L media) and highest yield (1.67mol H2/mol glucose). Two parameters were optimized through response surface methodology (RSM)-substrate concentration (3.0-5.0g/L) and initial pH (5.5-7.5), in a three-level factorial design. A total of 11 runs were performed in duplicate, which revealed that 4.0g/L substrate concentration and 6.5 initial pH were optimal in producing hydrogen. The metabolites produced were acetic, butyric, propionic, lactic and isobutyric acids. The volumetric H2 productions, without and with pH adjustments, were 1.24L H2/L media and 1.45L H2/L media, respectively.

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.

Surfactant assisted microwave irradiation pretreatment of corncob: Effect on hydrogen production capacity, energy consumption and physiochemical structure

The combination pretreatment strategy is an effective way to intensify photo-fermentative biohydrogen production (PFHP) process. In this study, the synergistic effects of microwave irradiation and surfactants on the hydrogen production performance, energy analysis and structural characteristics was evaluated. Results revealed that hydrogen production performance was improved after microwave irradiation pretreatment (MIP) and surfactants assisted microwave irradiation pretreatment (SMIP). SMIP group had a higher cumulative hydrogen yield (CHY) of 367.87 ± 6.481 mL compared with control group (223.26 ± 4.329 mL) and MIP group (303.66 ± 3.366 mL), which was an increase of 36.01% and 64.77%, respectively. Energy evaluation analysis showed that the energy ratio of SMIP (0.49) was higher than that of MIP (0.37) in the PFHP system, therefore, SMIP can save more energy. After SMIP, the corncob lignocellulose structure was greatly damaged, which was verified by SEM, FTIR, XRD and XPS analyses.

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.

Enhancement effect of defoamer additives on photo-fermentation biohydrogen production process

Foaming is a key issue should be solved in the process of photo-fermentation biohydrogen production (PFHP), since it has negative influence on the hydrogen yield potential, especially when taken straw as substrate. Appropriate foam control measures must be considered for industrialization. Hence, in this work, foam height and biohydrogen yield were selected as index, the effect of defoamer addition on PFHP was investigated. The defoamer has no negative effect on bacterial growth. In the addition range of 0–1 mL/L, the higher addition amount, indicates better foam control effect. The maximum foam height could be reduced by 55% and the foam existence time by 36 h. The reduction of foam was beneficial to biohydrogen production, and the highest cumulative hydrogen yield was increased 23% at the addition level of 0.125 mL/L.

Forecasting of reducing sugar yield from corncob after ultrafine grinding pretreatment based on GM(1,N) method and evaluation of biohydrogen production potential

Pretreatment of biomass helps to enhance reducing sugar yield from biomass during enzyme hydrolysis tests. Ultrafine grinding was applied to pretreat corncob. The effect of affecting factors including milling time, initial particle size and ball to power weight on the reducing sugar yield from corncob was investigated firstly. And then, an GM(1,N) model was constructed to model the ultrafine grinding pretreatment system predicting the reducing sugar yield from corncob based on experimental data, the results demonstrate GM(1,N) could predict the reducing sugar yield accurately and effectively without depending on the number of samples. The initial particle size was the most critical influential factor affecting reducing sugar yield according to the driving coefficient. The cumulative hydrogen yield was significantly affected by ultrafine grinding pretreatment, the hydrogen yield of pretreated corncob was 153.60 ± 5.8 mL/g total solids, which was higher than that of untreated corncob (113.20 ± 3.2 mL/g total solids).

Calcium Hypochlorite Promotes Dark Fermentative Hydrogen Production from Waste Activated Sludge

This study reported a high-efficiency and low-cost sludge pretreatment method using calcium hypochlorite [Ca(ClO)2] for promoting anaerobic fermentation performance. The experimental results indicated that the cumulative hydrogen yield was enhanced from 1.87 to 16.72 mL/g volatile suspended solids (VSSs) when the Ca(ClO)2 dosage was increased from 0 to 1.5 g/L and then reduced to 13.80 mL/g VSSs when the Ca(ClO)2 dosage reached 1.8 g/L. The mechanism study revealed that Ca(ClO)2 efficiently disrupted sludge extracellular polymeric substances and microbial cells, producing more soluble organics for the subsequent biochemical processes. Beyond that, the biodegradability of sludge organics was promoted by Ca(ClO)2 pretreatment. Biochemical reaction kinetic analysis indicated that the activities of microbes responsible for hydrogen consumption were severely inhibited when treated with Ca(ClO)2. The two decomposition products of Ca(ClO)2, Ca(OH)2 and HClO, positively affected the hydrogen yield, with the contribution of Ca(OH)2 being greater than HClO. Microbial community analysis illustrated that the fermentative microbes were markedly enriched by Ca(ClO)2 pretreatment, with the abundances found to be 3.21 and 45.62% in control and Ca(ClO)2-pretreated fermenters, respectively. After fermentation, the Ca(ClO)2-pretreated sludge showed better dewaterability than the control, and the organic pollutants diclofenac and sulfamethazine, as well as the fecal coliforms, were largely removed by Ca(ClO)2.

Surfactants-induced photo-fermentative biohydrogen production from corncob

Surfactants could improve the mass transfer capacity by avoiding agglomeration and sedimentation of substrate. This study evaluated the effects of diverse Tween series surfactants on hydrogen production performance of photo-fermentative biohydrogen production (PFHP) process. Tween 80 was found to be the most suitable surfactant. The maximum cumulative hydrogen yield (CHY) reached 49.38 ± 1.90 mL/g TS under 0.20% (v/v) Tween 80 addition. Highest energy recovery efficiency of 3.41 ± 0.13% and substrate conversion efficiency of 94.93 ± 0.44% were obtained, which was 50.37% and 1.7% higher than that of the control group, respectively. The effect of diverse Tween series surfactants on photosynthetic bacteria (PSB) was further studied. Results showed that Tween 80 significantly improved the growth and activity of PSB. The modified Han-Levenspiel model was adopted to analyze the effects of Tween 80 addition on PFHP. Results indicated that the reaction system was non-competitive inhibition, the predicted critical concentration of Tween 80 was 0.42% (v/v). This study provides a way to increase the CHY of corncob by the PFHP process.