Effect of initial substrate and biomass concentrations on anaerobic fermentative hydrogen production in batch reactors

The effects of initial substrate (5-60 g /L) and biomass concentration (0.5-3 g /L) on fermentative hydrogen production by mixed cultures were investigated in batch tests using glucose as substrate.The experimental results showed that the hydrogen production increases as the initial substrate concentration increases from 0 to 25 g /L.It indicated that the shift in the metabolic pathway or in the composition of the bacterial flora occurs.The maximum hydrogen yield of 1.78 mol /mol-glucose is obtained at the substrate concentration of 15 g /L.This study also shows that initial biomass concentration affects the hydrogen yield as the cumulative hydrogen production has been increased with the increase of initial cell concentration up to 1.5 g /L and reached the highest level.The maximum hydrogen yield is obtained at the cell concentration of 1.5 g /L.It indicated that the optimum biomass /substrate ratio,maximizing the hydrogen yield and the hydrogen production rate,is determined to be 0.1 g biomass /g glucose.

Influence of Metal Ions on Hydrogen Production by Photosynthetic Bacteria Grown in Escherichia coli Pre-Fermented Cheese Whey

The photosynthetic bacteria, Rodospirillum rubrum, produced hydrogen when grown in cheese whey in presence of light. The production increased three times as much when whey was used after being incubated in presence of Escherichia coli at 37℃ for 5 days, giving a total of 3600 ml of H2 in 10 days. The presence of Fe ions (5 mg/L) enhanced H2 production of treated whey to about 6000 ml in 10 days. Mo ions (0.3 and 1.6 mg/l) did not affect achieved H2 production of treated whey. However, when Fe and Mo ions were present together, the production was comparable with that of Mo ions alone, i.e. Mo prevented Fe of producing any enhancing effect. The addition of Mn ions (7.68 mg/L) to treated whey containing Fe (5 mg/L) and Mo ions (8 mg/L) increased H2 production to give about 9500 ml/10 days.

Optimization of Photo-Hydrogen Production by Immobilized Rhodopseudomonas Faecalis RLD-53

In this work, the optimization of hydrogen production by photo-fermentation bacteria immobilized on agar gel granule was systematic investigated in batch culture. Experiment focus on the effect of some important affecting factors on photo-hydrogen production. Results indicated that immobilized Rhodopseudomonas faecalis RLD-53 exhibited the highest hydrogen yield of 3.15 mol H2/mol acetate under follow optimal condition: agar granule diameter of 2.5 mm, inoculum age of 24 h, agar concentration of 2%, biomass of 4 mg/ml in agar and light intensity of 9000 lux. More importantly, immobilized photo-fermentation bacteria not only can enhance hydrogen production but can increase acids-tolerance capacity, even at pH 5.0 hydrogen also was produced, and thus hopefully immobilized photo-fermentation bacteria can be applied in the combination of dark and photo-fermentation for hydrogen production with high yield.

Effects of thermally pretreated temperature on bio-hydrogen production from sewage sludge

Hydrogen can be obtained by anaerobic fermentation of sewage sludge. Therefore, in this paper the effects of thermally pretreated temperatures on hydrogen production from sewage sludge were investigated under different pre-treatment conditions. In the thermal pretreatment, some microbial matters of sludge were converted into soluble matters from insoluble ones. As a result, the suspended solid（SS） and volatile suspended solid（VSS） of sludge decreased and the concentration of soluble COD（SCOD） increased, including soluble carbohydrates and proteins. The experimental results showed that all of those pretreated sludge could produce hydrogen by anaerobic fermentation and the hydrogen yields under the temperatures of 121℃ and 50℃ were 12.23 ml/g VS（most） and 1.17 ml/g VS （least）, respectively. It illuminated that the hydrogen yield of sludge was affected by the thermally pretreated temperatures. Additionally, the endurance of high hydrogen yield depended on the translation of microbial matters and inhibition of methanogens in the sludge. The temperatures of 100℃ and 121℃ （treated time, 30 min） could kill or inhibit completely the methanogens while the others could not. To produce hydrogen and save energy, 100℃ was chosen as the optimal temperature for thermal pretrcatment. The composition changes in liquid phase in the fermentation process were also discussed. The SCOD of sludge increased, which was affected by the pretreatment temperature. The production of volatile fatty acids in the anaerobic fermentation increased with the pretreatment temperature.

Effects of brewers' spent grain protein hydrolysates on gas production, ruminal fermentation characteristics, microbial protein synthesis and microbial community in an artificial rumen fed a high grain diet

Background: Brewers' spent grain(BSG) typically contains 20% – 29% crude protein(CP) with high concentrations of glutamine, proline and hydrophobic and non-polar amino acid, making it an ideal material for producing valueadded products like bioactive peptides which have antioxidant properties. For this study, protein was extracted from BSG, hydrolyzed with 1% alcalase and flavourzyme, with the generated protein hydrolysates(AlcH and FlaH)showing antioxidant activities. This study evaluated the effects of AlcH and FlaH on gas production, ruminal fermentation characteristics, nutrient disappearance, microbial protein synthesis and microbial community using an artificial rumen system(RUSITEC) fed a high-grain diet.Results: As compared to the control of grain only, supplementation of FlaH decreased(P < 0.01) disappearances of dry matter(DM), organic matter(OM), CP and starch, without affecting fibre disappearances;while AlcH had no effect on nutrient disappearance. Neither AlcH nor FlaH affected gas production or VFA profiles, however they increased(P < 0.01) NH_3-N and decreased(P < 0.01) H_2 production. Supplementation of FlaH decreased(P < 0.01)the percentage of CH_4 in total gas and dissolved-CH_4(dCH_4) in dissolved gas. Addition of monensin reduced(P < 0.01) disappearance of nutrients, improved fermentation efficiency and reduced CH_4 and H_2 emissions.Total microbial nitrogen production was decreased(P < 0.05) but the proportion of feed particle associated(FPA) bacteria was increased with FlaH and monensin supplementation. Numbers of OTUs and Shannon diversity indices of FPA microbial community were unaffected by AlcH and FlaH;whereas both indices were reduced(P < 0.05) by monensin. Taxonomic analysis revealed no effect of AlcH and FlaH on the relative abundance(RA) of bacteria at phylum level, whereas monensin reduced(P < 0.05) the RA of Firmicutes and Bacteroidetes and enhanced Proteobacteria. Supplementation of FlaH enhanced(P < 0.05) the RA of genus Prevotella, reduced Selenomonas, Shuttleworthia, Bifidobacterium and Dialister as compared to control;monensin reduced(P < 0.05) RA of genus Prevotella but enhaced Succinivibrio.Conclusions: The supplementation of FlaH in high-grain diets may potentially protect CP and starch from ruminal degradation, without adversely affecting fibre degradation and VFA profiles. It also showed promising effects on reducing CH_4 production by suppressing H_2 production. Protein enzymatic hydrolysates from BSG using flavourzyme showed potential application to high value-added bio-products.

Progress and Prospects of Hydrogen Production: Opportunities and Challenges

This study presents an overview of the current status of hydrogen production in relation to the global requirement for energy and resources.Subsequently,it symmetrically outlines the advantages and disadvantages of various production routes including fossil fuel/biomass conversion,water electrolysis,microbial fermentation,and photocatalysis(PC),in terms of their technologies,economy,energy consumption,and costs.Considering the characteristics of hydrogen energy and the current infrastructure issues,it highlights that onsite production is indispensable and convenient for some special occasions.Finally,it briefly summarizes the current industrialization situation and presents future development and research directions,such as theoretical research strengthening,renewable raw material development,process coupling,and sustainable energy use.

Comparison of ASBR and CSTR reactor for hydrogen production from palm oil mill effluent under thermophilic condition

Hydrogen production from palm oil mill effluent (POME) by Thermoanaerobacterium thermosaccharolyticum PSU-2 was investigated both in batch and continuous reactors using anaerobic sequencing batch reactor (ASBR) and continuous stirred tank reactor (CSTR). The hydrogen production determined from batch experiment of POME at an inoculum size of 0%, 10%, 20% and 30% (v/v) was 161, 201, 246 and 296 mL H2/g-COD with COD removal efficiency of 21%, 23%, 23% and 23%, respectively. Continuous hydrogen production was start-up with 30% (v/v) inoculum in both ASBR and CSTR reactors and more than 30% COD removal could be obtained at HRT of 4 days, corresponding to OLR of 11.3 g COD/ L·day. Similar hydrogen production rates of 2.05 and2.16 LH2/L. day were obtained from ASBR and CSTR, respectively. COD removal efficiency of ASBR was 37.7%, while it was 44.8% for CSTR. However, ASBR was stable in term of alkalinity, while the CSTR was stable in term of hydrogen production, soluble metabolites concentration and alkalinity. Therefore, the CSTR was found to be more stable in hydrogen production than ASBR under the same OLR.

Gas Chromatography as an Analytical Monitoring Technique for Hydrogen Production from Spirulina maxima 2342

Hydrogen (H2) production from experiments with Spirulina maxima 2342 is reported in this work. The performance of this photosynthetic microorganism for producing H2 was evaluated for the first time under specific experimental conditions (e.g., a biomass concentration of 0.34 ± 0.02 g, a light intensity of 150 μE.s-1.m-2 and reaction times of 19.3 ± 1.2 h). The performance of this photosynthetic microorganism for producing hydrogen was successfully improved by the addition of sodium dithionite (a reducing agent) as an innovative method for increasing the gas production, and as a main contribution of this work. Quantitative gas chromatography (GC) analyses of H2 to verify the production performance were successfully carried out at low concentration levels. GC analyses were performed by means of a conventional thermal conductivity detector coupled to a separation system of a Molecular Sieve column 500 mm × 3175 mm (L × ID). Low detection limits were consistently obtained with the GC system used. The separation of H2 in culture samples was efficiently achieved in average retention times of 1.47 min. The H2 produced in this process was subsequently used for power generation using a Proton Exchange Membrane Fuel Cell (PEMFC).

Hydrogen energy recovery from high strength organic wastewater with ethanol type fermentation using acidogenic EGSB reactor

A lab-scale expanded granular sludge bed （EGSB） reactor was employed to evaluate the feasibility of the hydrogen energy recovery potential from high strength organic wastewater. The results showed that a maximum hydrogen production rate of 7.43 m3 H2/m3 reactor·d and an average hydrogen production rate of 6.44 m3 H2/m3 reactor·d were achieved with the hydrogen content of 50%～56% in the biogas during the 90-day operation. At the acidogenic phase, COD removal rate was stable at about 15%. In the steady operation period, the main liquid end products were ethanol and acetic acid, which represented ethanol type fermentation. Among the liquid end products, the concentration percentage of ethanol and acetic acid amounted to 69.5%～89.8% and the concentration percentage of ethanol took prominent about 51.7%～59.1%, which is better than the utilization of substrate for the methanogenic bacteria. An ethanol type fermentation pathway was suggested in the operation of enlarged industrial continuous hydrogen bio-producing reactors.

Evaluating the impact of sulfamethoxazole on hydrogen production during dark anaerobic sludge fermentation

The impact of antibiotics on the environmental protection and sludge treatment fields has been widely studied.The recovery of hydrogen from waste activated sludge(WAS)has become an issue of great interest.Nevertheless,few studies have focused on the impact of antibiotics present in WAS on hydrogen production during dark anaerobic fermentation.To explore the mechanisms,sulfamethoxazole(SMX)was chosen as a representative antibiotic to evaluate how SMX influenced hydrogen production during dark anaerobic fermentation of WAS.The results demonstrated SMX promoted hydrogen production.With increasing additions of SMX from 0 to 500 mg/kg TSS,the cumulative hydrogen production elevated from 8.07±0.37 to 11.89±0.19 mL/g VSS.A modified Gompertz model further verified that both the maximum potential of hydrogen production(Pm)and the maximum rate of hydrogen production(R_(m))were promoted.SMX did not affected sludge solubilization,but promoted hydrolysis and acidification processes to produce more hydrogen.Moreover,the methanogenesis process was inhibited so that hydrogen consumption was reduced.Microbial community analysis further demonstrated that the introduction of SMX improved the abundance of hydrolysis bacteria and hydrogen-volatile fatty acids(VFAs)producers.SMX synergistically influenced hydrolysis,acidification and acetogenesis to facilitate the hydrogen production.

Effect of different gas releasing methods on anaerobic fermentative hydrogen production in batch cultures

Decreasing hydrogen partial pressure can not only increase the activity of the hydrogen enzyme but also decrease the products inhibition, so it is an appropriate method to enhance the fermentative hydrogen production from anaerobic mixed culture. The effect ofbiogas release method on anaerobic fermentative hydrogen production in batch culture system was compared, i.e., Owen method with intermediately release, continuous releasing method, and continuous releasing ＋ CO2 absorbing. The experi- mental results showed that, at 35℃, initial pH 7.0 and glucose concentration of 10 g.L-1, the hydrogen produc- tion was only 28 mL when releasing gas by Owen method, while it increased two times when releasing the biogas continuously. The cumulative hydrogen production could reach 155 mL when carbon dioxide in the gas stream was continuously absorbed by 1 mol.L-1 NaOH. The results showed that acetate was dominated, accounting for 43% in the dissolved fermentation products in Owen method, whereas the butyrate predominated and reached 47%-53% of the total liquid end products when releasing gas continuously. It is concluded that the homoacetogenesis could be suppressed when absorbing CO2 in the gas phase in fermentative hydrogen production system.

Recent progress on rational design of catalysts for fermentative hydrogen production

The increasingly severe energy crisis has strengthened the determination to develop environmentally friendly energy.And hydrogen has emerged as a candi-date for clean energy.Among many hydrogen generation methods,biohydrogen stands out due to its environmental sustainability,simple operating environ-ment,and cost advantages.This review focuses on the rational design of catalysts for fermentative hydrogen production.The principles of microbial dark fermen-tation and photo-fermentation are elucidated exhaustively.Various strategies to increase the efficiency of fermentative hydrogen production are summa-rized,and some recent representative works from microbial dark fermentation and photo-fermentation are described.Meanwhile,perspectives and discussions on the rational design of catalysts for fermentative hydrogen production are provided.

太阳能光热催化制氢研究进展

太阳能光热催化(SPTC)制氢技术是从遵循全光谱太阳能分波段能量禀赋特性出发,利用太阳能短波部分高品位光子的光效应驱动光催化反应,同时利用长波部分低品位光子的热效应驱动热催化反应或者辅助强化光催化制氢,可解决传统热催化的高能耗和光催化的低转化效率问题,实现全光谱太阳能的分波段协调转化高效制氢。本文首先介绍了SPTC的定义与分类,然后详细综述了热效应对光催化以及光效应对热催化的协同强化机制,最后对SPTC技术的发展前景进行展望,以期为该技术更广泛的研究及应用提供指导。

Delignification of disposable wooden chopsticks waste for fermentative hydrogen production by an enriched culture from a hot spring

Hydrogen （H2） production from lignocellulosic materials may be enhanced by removing lignin and increasing the porosity of the material prior to enzymatic hydrolysis. Alkaline pretreatment conditions, used to delignify disposable wooden chopsticks （DWC） waste, were investigated. The effects of NaOH concentration, temperature and retention time were examined and it was found that retention time had no effect on lignin removal or carbohydrate released in enzymatic hydrolysate. The highest percentage of lignin removal （41%） was obtained with 2% NaOH at 100℃, correlated with the highest carbohydrate released （67 mg/gpretreated DWC） in the hydrolysate. An enriched culture from a hot spring was used as inoculum for fermentative H2 production, and its optimum initial pH and temperature were determined to be 7.0 and 50℃, respectively. Furthermore, enzymatic hydrolysate from pretreated DWC was successfully demonstrated as a substrate for fermentative H2 production by the enriched culture. The maximum H2 yield and production rate were achieved at 195 mL H2/g total sugarsconsumed and 1 16 mL Hz/（L.day）, respectively.

光热协同甲醇水蒸气重整制氢实验和微观机理研究

针对太阳能光热化学甲醇重整制氢中光热耦合效应及微观机理尚不清楚的问题,采用光热化学和热化学反应对比的研究方式,与微观实验相结合,研究了光热化学甲醇重整中光和热的耦合效应,探究了光和热在微观产物转化中的反应路径。研究结果表明:在较低温度下,光对氢气产率的提升具有促进作用,当其与热化学达到相同氢气产率时,光热化学反应温度降低,造成这种现象的原因是光促进了水的分解、吸附态HCOO*的生成以及碳酸盐的分解,其中水在反应中的作用通过不同水醇比的实验得到了进一步验证;随着温度的升高,固定辐照度下光的促进作用逐渐降低,这是因为光对碳酸盐物质分解的促进作用随温度升高而减弱。研究阐明了光和热的耦合效应,分析了对应的微观机理,为理解光热协同机理提供了理论基础。

连续流Biohydrogenbacterium R3 sp.nov.菌株糖蜜废水发酵产氢能力分析

以从连续流搅拌槽式反应器(CSTR)内的活性污泥中分离出的高效厌氧产氢菌BiohydrogenbacteriumR3 sp.nov.为发酵产氢微生物,糖蜜废水为发酵底物,试验分析了连续流发酵法R3菌株的产氢效能。结果表明:在温度36℃、水力停留时间6 h、进水COD在2 600～4 440 mg/L范围内变化,CSTR反应器可实现连续稳定产氢,并且分别得到最大产气量和产氢量为6.08 L和3 L;进水底物质量浓度的变化,对系统产氢效能的影响十分明显。进水pH值的降低影响系统的COD去除效率,但对出水pH值却无明显影响,可见,R3菌株纯培养CSTR是一个相对稳定的发酵制氢系统,系统氧化还原电位稳定在-445～-420 mV。

“双碳”下金属纳米颗粒优化暗发酵制氢策略及前景

氢能是“双碳”下推动化石能源低碳转型的重要方向,推动绿氢技术的发展仍面临诸多挑战,微生物暗发酵制氢是实现生物质绿氢转化的有效途径。其中,利用具有量子尺寸效应、比表面积大和电导率高的金属纳米颗粒(MNPs)优化暗发酵制氢技术是近年来的研究热点。综述和评论了国内外添加MNPs用于优化暗发酵制氢性能的作用机制、技术难点和制氢效果等,重点阐述并比较了铁、镍和锌基三类热门MNPs优化策略在提高产氢酶系活性、增强代谢产氢途径和优化微生物群落结构等方面的作用,展望了暗发酵制氢可深入MNPs优化氢化酶活性、拓宽生物质发酵底物以及产氢菌筛选和反应器设计、生物质发酵技术开发等研究方向和应用前景。

嗜热厌氧菌共培养发酵玉米秸秆产氢的研究

氢能是对环境无害且可以替代化石燃料的可持续性能源。利用嗜热厌氧菌暗发酵木质纤维素生产氢气是一种极具潜力的生物制氢技术,具有清洁、高效和可再生的优势。构建解糖热解纤维素菌和热解糖厌氧杆菌共培养体系,考察两株菌株接种比例、总接种量和底物浓度对玉米秸秆发酵产氢的影响。实验结果表明,在发酵体系初始pH值7.0,培养温度60℃条件下,当解糖热解纤维素菌和热解糖厌氧杆菌接种比例为3∶2,菌种总接种量为6%,秸秆浓度为15 g·L^(-1)时,体系产氢能力最强。此时,发酵体系产氢量累积达到65.6 mL·g-1-秸秆,氢气含量为46.9%,最大产氢速率为1.47 mL·g^(-1)h^(-1)。

微藻光—暗联合发酵制氢固碳效果及经济效益评价

微藻能源是最具潜力的第三代生物质能源,将废物处理的微藻用于制氢,能够在增强废物资源化利用的同时提升生物制氢的经济效益与环境效益。为优化微藻生物制氢的方式并提升生产效益,基于光伏供能情境,采用光—暗发酵相结合的方式进行了微藻生物氢的制取,并分析了不同光—暗联合下微藻的制氢效果和固碳减排效果,最后核算了废物处理产生的经济效益和生物制氢的生产潜力。研究结果表明:①微藻光发酵制氢具有较好的固碳减排效果,每生产1 kg氢气,光发酵的固碳减排量为0.89 kgCO_(2),相较于暗发酵高0.46 kgCO_(2);②暗发酵制氢具有较好的经济效益,每生产1 kg氢气,暗发酵制氢的经济效益为61.56元,相较于光发酵高61.01元;③将光—暗发酵相结合,单个周期可生产41.23 kg氢气,实现固碳减排54.61 kgCO_(2),产生经济效益为2560.52元。结论认为:①采用TP5类(自养时间7 d、异养时间9 d,微藻最终浓度为54 g/L)周期下微藻增殖量进行的光—暗发酵制氢,实现了固碳减排与经济效益并存,相比于其他组合具有更好的生产效果,更适合用于规模化扩大生产;②光—暗发酵联合制氢是基于微藻增殖所进行的,应依据藻种特性优化制氢环境,对制氢比例与制氢方式做出调整,以加强微藻生物质能源开发,不断扩展微藻生物制氢的发展前景。