Recent advances in reuse of waste material as substrate to produce biohydrogen by purple non-sulfur (PNS) bacteria

Hydrogen is the fuel of the future mainly due to its high conversion efficiency, recyclability and non-polluting nature. Biological hydrogen production processes, mostly mediated photosynthetic bacteria, are more favorable candidates for biological hydrogen production due to their high conversion efficiency and versatility in the substrates (including wastewater) they can utilize. The potential utilization of waste material is being investigated extensively with suitable bioprocess technologies for providing cheaper raw materials with simultaneous waste treatment and bioremediation. Thus, this review article summarizes the biohydrogen production metabolism of purple non-sulfur (PNS) bacteria and research works involving biohydrogen production using various wastes such as tofu wastewater, palm oil mill effluent, olive mill wastewater, brewery wastewater, etc. by photosynthetic PNS bacteria. Waste materials used, yields and rates are reviewed, together with a discussion of the economics and perspectives of biohydrogen production from waste materials.     

Single stage photofermentative hydrogen production from glucose: An attractive alternative to two stage photofermentation or co-culture approaches

Photosynthetic bacteria have been extensively investigated for biohydrogen production due to their high intrinsic substrate conversion efficiency. Many studies have examined different aspects of photo fermentative hydrogen production using various volatile organic fatty acids under nitrogen limited conditions, and in some cases nearly stoichiometric hydrogen yields have been obtained. In addition, there has been great interest in using photosynthetic bacteria to increase the yields of dark fermentation of glucose through either two stage or co-culture approaches. Although these processes can achieve yields of about 7 mol of H₂ per mole of glucose, there have many drawbacks. Thus, we have begun the systematic investigation of a simple one stage system for the conversion of glucose to hydrogen through photofermentation by Rhodobacter capsulatus. Yields of about 3 mol of H₂ per moles of glucose have been obtained, which represents a yield of 25% yield. Thus improvement is needed and can be sought through a variety of means, including. process optimization and gene inactivation. These approaches could allow the development of a single stage process for the complete stoichiometric conversion of glucose, or glucose containing wastes, to hydrogen with a minimal lag phase and relative insensitivity to inhibition by fixed nitrogen. This would present an attractive simple alternative to either two stage or co-culture fermentations for the complete conversion of carbohydrate substrates to hydrogen.     

海洋光合菌群利用乙酸产氢的实验研究

通过富集获得产氢海洋光合菌群,该菌群可以有效利用发酵产氢的关键副产物乙酸作为产氢碳源.温度、光照强度、起始pH和乙酸浓度都对该菌群产氢和生长有明显影响.当在30℃、4000lx光照和起始pH=8.0的条件下培养时,此光合菌群产氢量和底物转化效率较高.乙酸浓度对产氢影响巨大,低浓度乙酸的底物转化效率较高,但总产氢量不高;高浓度乙酸的底物转化效率不高,但总产氢量较高.此实验结果为海洋光合细菌与海洋发酵细菌偶联产氢提供科学参考.     

Towards a super H2 producer: Improvements in photofermentative biohydrogen production by genetic manipulations

Photofermentative hydrogen production by purple non-sulfur bacteria is a potential candidate among biological hydrogen production methods. Hydrogen is produced under anaerobic conditions in light using different organic substrates as carbon source. The hydrogen evolution occurs mainly through the catalytic activity of the nitrogenases under non-repressive concentrations of ammonia. However, total hydrogen production is constrained due to several reasons in purple non-sulfur (PNS) bacteria, such as consumption of hydrogen by uptake hydrogenase, inefficient hydrogen production capacity of nitrogenase, limited electron flow to the nitrogenase, sensitivity of nitrogenase towards ammonia, etc. Hence, PNS bacteria need to be manipulated genetically to overcome these limitations and to make the process practically feasible. This review focuses on various approaches for the genetic improvement of biohydrogen production by PNS bacteria.     

Hydrogen production from simultaneous saccharification and fermentation of lignocellulosic materials in a dual-chamber microbial electrolysis cell

In this work, a dual-chamber microbial electrolysis cell (MEC) with concentric cylinders was fabricated to investigate hydrogen production of three different lignocellulosic materials via simultaneous saccharification and fermentation (SSF). The maximal hydrogen production rate (HPR) was 2.46 mmol/L/D with an energy recovery efficiency of 215.33 % and a total energy conversion efficiency of 11.29 %, and the maximal hydrogen volumetric yield was 28.67 L/kg from the mixed substrate. The concentrations of reducing sugar and organic acids, the pH, and the current in the MEC system during hydrogen production were monitored. The concentrations of reducing sugar, butyrate, lactate, formate, and acetate initially increased during SSF and then decreased due to hydrogen production. Moreover, the highest current was obtained from the mixed substrate, which means that the mixed substrates are beneficial to microbial growth and metabolism. These results suggest that lignocellulosic materials can be used as substrate in a low-energy-input dual-chamber MEC system for hydrogen production.     

Biological hydrogen production; fundamentals and limiting processes

Biological hydrogen production has been known for over a century and research directed at applying this process to a practical means of hydrogen fuel production has been carried out for over a quarter century. The various approaches that have been proposed and investigated are reviewed and critical limiting factors identified. The low energy content of solar irradiation dictates that photosynthetic processes operate at high conversion efficiencies and places severe restrictions on photobioreactor economics. Conversion efficiencies for direct biophotolysis are below 1% and indirect biophotolysis remains to be demonstrated. Dark fermentation of biomass or wastes presents an alternative route to biological hydrogen production that has been little studied. In this case the critical factor is the amount of hydrogen that can be produced per mole of substrate. Known pathways and experimental evidence indicates that at most 2–3 mol of hydrogen can be obtained from substrates such as glucose. Process economics require that means be sought to increase these yields.     

Biohydrogen production by a mixed photoheterotrophic culture obtained from a Winogradsky column prepared from the sediment of a southern Brazilian lagoon

The potential of a photoheterotrophic mixed culture isolated from a Winogradsky column prepared with the sediment of Lagoa da Conceição, a lagoon situated in Florianópolis – Brazil, was evaluated with respect to hydrogen production. Partial characterization of the mixed culture was carried out by spectrophotometric analysis of the whole cell pigment and molecular analysis by PCR/DGGE. Hydrogen production from acetate and butyrate as carbon source and sodium glutamate as nitrogen source was accomplished in batch culture conducted in 10 mL bottles, at 30 °C, for 10 days, under light intensity of 5.86 W/m². The results showed the presence of bacteriochlorophyll a and carotenoids in the mixed culture, both of which are pigments present in the photosystem of purple non-sulfur (PNS) bacteria. DGGE analysis revealed four distinct bands corresponding to different sequences of 16S rDNA, thus suggesting the presence of four prokaryotic species. Hydrogen production from acetate and butyrate was observed. Maximum hydrogen production (143.56 mL/L and 135.41 mL/L for acetate and butyrate, respectively) and hydrogen production rates (0.60 mL/L h and 0.56 mL/L h for acetate and butyrate, respectively) were similar for both substrates, but acetate was 24% more efficient than butyrate in terms of substrate conversion into hydrogen. The results of this study are very promising, since a selected culture able to grow and produce hydrogen from two substrates with similar productivity was obtained via a simple methodology.     

Anthrahydroquinone-2,6-disulfonate increases the rate of hydrogen production during Clostridium beijerinckii fermentation with glucose,xylose, and cellobiose

Fermentative hydrogen production is considered a reasonable alternative for generating H₂ as an energy carrier for electricity production using hydrogen fuel cells. The kinetics of hydrogen production from glucose, xylose and cellobiose were investigated using pure culture Clostridium beijerinckii NCIMB 8052. Adding anthrahydroquinone-2,6-disulfonate (AH₂QDS) at concentrations ranging from 100 μM to 500 μM increased the hydrogen production rates from 0.80 to 1.35 mmol/L-hr to 1.20–2.70 mmol/L-hr with glucose, xylose, or cellobiose as the primary substrates. AH₂QDS amendment also increased the substrate utilization rate and biomass growth rate by at least two times. These findings suggest that adding hydroquinone reducing equivalents influence cellular metabolism with hydrogen production rate, substrate utilization rate, and growth rate being simultaneously affected. Resting cell suspensions were conducted to investigate the influence of AH₂QDS on the hydrogen production rate from glyceraldehyde 3-phosphate, which is a shared intermediate in both glycolysis and pentose phosphate pathway. Data demonstrated that hydrogen production rate increased by 1.5 times when glyceraldehyde 3-phosphate was the sole carbon source, suggesting that the hydroquinone may alter reactions starting with or after glyceraldehyde 3-phosphate in central metabolism. These data demonstrate that adding hydroquinones increased overall metabolic activity of C. beijerinckii. This will eventually increase the efficiency of industrial scale production once appropriate hydroquinone equivalents are identified that work well in large-scale operations, since fermentation rate is one of the two critical factors (production rate and yield) influencing efficiency and cost.     

Hydrogen production by combining two types of photosynthetic bacteria with different characteristics

The double-layer photobioreactor using two types of photosynthetic bacteria, Rhodobacter sphaeroides RV and its reduced-pigment mutant, MTP4, was developed for efficient hydrogen production. The two types of bacteria had different characteristics on light energy, hydrogen production rate and conversion efficiency. MTP4 produced hydrogen more efficiently under high light conditions and RV did so under low light conditions. Illuminated light toward the surface of a photobioreactor quasi-exponentially declines as it penetrates into the reactor. When two types of bacteria were placed using the developed reactor according to this light distribution, the hydrogen production rate reached 3.64 l/m²/h at a light intensity of 500 W/m² in 24 h and the conversion efficiency of light energy to hydrogen was 2.18%. These values were 33% higher than those of only using RV. The low light in the deep part of the reactor was utilized efficiently, resulting in a higher hydrogen production rate.     

Hydrogen amplification from coke oven gas using a CO2 adsorption enhanced hydrogen amplification reactor

To improve coke oven gas (COG) energy conversion, alternative configurations for amplifying hydrogen from COG are proposed in this paper. In these new configurations, a CO₂ adsorption enhanced hydrogen amplification reactor is combined with a pressure swing adsorption separation unit (PSA) to produce pure hydrogen. Hydrogen production was integrated with desorption gas utilization, in situ CO₂ capture and waste heat recovery to improve COG energy conversion efficiency and decrease CO₂ emissions. To analyze the advantages of the flowsheet modifications, technical and economic performance indicators were used to evaluate and compare the performances of the various system configurations. Simulation results show that the alternative configurations proposed in this paper have higher energy conversion efficiencies, higher hydrogen yields and shorter dynamic payback periods. The variation of technical performance with reaction temperature, pressure, sorbent to carbon ratio and steam to carbon ratio were also analyzed using a sensitivity study. Optimal operating conditions for the CO₂ adsorption enhanced hydrogen amplification reactor were obtained based on the simulation results.     

Photofermentative molecular biohydrogen production by purple-non-sulfur (PNS) bacteria in various modes: The present progress and future perspective

Hydrogen is green fuel for the future, mainly due to its recyclability. Biohydrogen production processes are less energy intensive and environmental friendly in compared to chemical processes. Fermentative biohydrogen production can be broadly classified as: dark and photo fermentation. Two enzymes, nitrogenase and hydrogenase play important role in biohydrogen production. Purple Non-Sulfur bacteria (PNS) are mainly used in photofermentative hydrogen production through which the overall yield can be improved manifolds. The scope and objective of this review paper is to investigate the performance of various light driven photofermentative hydrogen production by PNS bacteria along with several developmental works related to batch, repeated batch, feed batch and continuous operation. However the study of Photobiological process by microalgae or cyanobacteria is outside the scope of this review. Optimization of suitable process parameters such as carbon and nitrogen ratio, illumination intensity, bioreactor configuration, immobilization of active cells in specific continuous mode and inoculum age may lead to higher yield of hydrogen generation.     

Solar to chemical conversion using metal nanoparticle modified microcrystalline silicon thin film photoelectrode

Microcrystalline silicon (μc-Si:H) thin films, which are prospective low-cost semiconductor materials, are used as photoelectrodes for the direct conversion of solar energy to chemical energy. An n-type microcrystalline cubic silicon carbide layer and an intrinsic μc-Si:H layer are deposited on glassy carbon substrates using the hot-wire cat-CVD method. The μc-Si:H electrodes are modified with platinum nanoparticles through electroless displacement deposition. The electrodes produce hydrogen gas and iodine via photoelectrochemical decomposition of hydrogen iodide with no external bias under solar illumination. Surface modification with platinum nanoparticles and surface termination with iodine improve the conversion efficiency.     

Cogeneration of hydrogen and methane from Arthrospira maxima biomass with bacteria domestication and enzymatic hydrolysis

The energy conversion efficiency in hydrogen and methane cogeneration from Arthrospira maxima biomass by two-phase fermentation is improved with bacteria domestication and enzymatic hydrolysis. The A. maxima biomass (dried weight) can theoretically cogenerate hydrogen and methane yields of 318 ml/g and 262 ml/g, which dramatically increases the theoretical energy conversion efficiency from 16.6% in hydrogen only production to 61.9%. The experimental hydrogen yield is increased from 49.7 ml/g to 64.3 ml/g, when the hydrogenogens community is domesticated with A. maxima biomass as carbon source. The hydrogen yield is further increased to 78.7 ml/g when A. maxima biomass is hydrolyzed with glucoamylase, which gives an energy conversion efficiency of 4.1% in hydrogen only production. The soluble metabolite byproducts from the first hydrogen-producing phase are reutilized by methanogens to produce methane of 109.5-145.5 ml/g in the second phase. The cogeneration of hydrogen and methane from A. maxima biomass markedly increases the experimental energy conversion efficiency to 27.7%.     

A review of catalytic hydrogen production processes from biomass

Hydrogen is believed to be critical for the energy and environmental sustainability. Hydrogen is a clean energy carrier which can be used for transportation and stationary power generation. However, hydrogen is not readily available in sufficient quantities and the production cost is still high for transportation purpose. The technical challenges to achieve a stable hydrogen economy include improving process efficiencies, lowering the cost of production and harnessing renewable sources for hydrogen production. Lignocellulosic biomass is one of the most abundant forms of renewable resource available. Currently there are not many commercial technologies able to produce hydrogen from biomass. This review focuses on the available technologies and recent developments in biomass conversion to hydrogen. Hydrogen production from biomass is discussed as a two stage process – in the first stage raw biomass is converted to hydrogen substrate in either gas, liquid or solid phase. In the second stage these substrates are catalytically converted to hydrogen.     

A Survey on Various Carbon Sources for Biological Hydrogen Production via the Water-Gas Reaction Using a Photosynthetic Bacterium (Rhodospirillum rubrum)

Growth model of anaerobic photosynthetic bacteria on various carbon sources for fermentative hydrogen production growth from synthesis gas was investigated. It was found that the rate of utilization of carbon monoxide (CO) by Rhodospirillum rubrum on acetate was growth related. A biologically based water-gas shift reaction was catalyzed by the specific bacterium at ambient temperature to convert the gaseous substrate, CO to carbon dioxide, while simultaneously convert water to a useful product, molecular hydrogen. Experiments were conducted to measure the specific CO uptake and hydrogen production rates. Also, effect of initial organic substrate concentration was investigated. The microorganism was grown on formate, acetate, malate, glucose, fructose, and sucrose. The modified Teissier and Contois equations were further developed for the growth model based on existing theory and experimental data. It was also found that the improvement in the yield of hydrogen production using acetate as a suitable substrate for R. rubrum, resulted in 0.87 mmole H ₂ /mmole CO. The obtained hydrogen yield of R. rubrum on acetate was 87% of stoichiometric conversion. The main objective of this research was to demonstrate that the biological hydrogen production may efficiently be implemented as an alternative energy for fossil fuel replacement in the future.     

Hydrogen productivity of photosynthetic bacteria on dark fermenter effluent of potato steam peels hydrolysate

Hydrogen productivities of different photosynthetic bacteria have been searched on real thermophilic dark fermentation effluents (DFE). The results obtained with potato steam peels hydrolysate (PSP) DFE were compared to glucose DFE. Photobiological hydrogen production has been carried out in indoor, batch photobioreactors using several strains of purple non-sulfur (PNS) bacteria such as Rhodobacter capsulatus (DSM1710), Rhodobacter capsulatus hup- (YO3), Rhodobacter sphaeroides O.U.001 (DSM5864), Rb. sphaeroides O.U.001 hup- and Rhodopseudomonas palustris.The efficiency of photofermentation depends highly on the composition of the effluent and the PNS bacterial strain used. Rb. sphaeroides produced the highest amount of hydrogen on glucose DFE. Rb. capsulatus gave better results on PSP DFE. This study demonstrates that photobiological hydrogen production with high efficiency and productivity is possible on thermophilic dark fermentation effluents. Consequently, a sequential operation of dark fermentation and photofermentation is a promising route to produce hydrogen, and it provides a higher hydrogen yield compared to single step processes.     

Thermodynamic analysis of a membrane-assisted chemical looping reforming reactor concept for combined H2 production and CO2 capture

There is great consensus that hydrogen will become an important energy carrier in the future. Currently, hydrogen is mainly produced by steam reforming of natural gas/methane on large industrial scale or by electrolysis of water when high-purity hydrogen is needed for small-scale hydrogen plants. Although the conventional steam reforming process is currently the most economical process for hydrogen production, the global energy and carbon efficiency of this process is still relatively low and an improvement of the process is key for further implementation of hydrogen as a fuel source. Different approaches for more efficient hydrogen production with integrated CO₂ capture have been discussed in literature: Chemical Looping Combustion (CLC) or Chemical Looping Reforming (CLR) and membrane reactors have been proposed as more efficient alternative reactor concepts relative to the conventional steam reforming process. However, these systems still present some drawbacks. In the present work a novel hybrid reactor concept that combines the CLR technology with a membrane reactor system is presented, discussed and compared with several other novel technologies. Thermodynamic studies for the new reactor concept, referred to as Membrane-Assisted Chemical Looping Reforming (MA-CLR), have been carried out to determine the hydrogen recovery, methane conversion as well as global efficiency under different operating conditions, which is shown to compare quite favorably to other novel technologies for H₂ production with CO₂ capture.     

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).     

Experimental investigation of various copper oxide electrodeposition conditions on photoelectrochemical hydrogen production

In this study, an experimental investigation of photosensitive material copper oxide electrodeposition on various substances is performed under different experimental conditions in order to evaluate the effects on photoelectrochemical hydrogen production system. The experimental setup consists of solar simulator, electrodeposition chemicals, hydrogen sensor, pH meter, graphite and platinum electrodes, heating plate, stirrer, temperature sensors, cathode and anode plates, concentrating lens and potentiostat. The overall aim is to optimize the efficiencies by generating higher currents and eventually hydrogen as light enhances the separation of water process. The results obtained in this study are promising for photoelectrochemical hydrogen production under the solar simulator and concentrated light irradiation conditions. Furthermore, an electrolysis setup using the coated metals and graphite rod is built to investigate the amount of photocurrent production. The characterization is also conducted under light and no-light conditions, where the amount of produced current and hydrogen increased in light compared to no-light condition. At the applied voltage of ?0.6 V and ?0.4 V vs. Ag/AgCl, the photocurrent densities of 0.8 mA/cm² and 0.27 mA/cm² are obtained with a solar conversion efficiency of 0.86% and 0.24%, respectively.     

Thermophilic biohydrogen production for commercial application: the whole picture

Hydrogen is a promising alternative to fossil fuel for a source of clean energy. Thermophilic biohydrogen production is beneficial for obtaining high H₂ production yield. This review recapitulates the basic metabolic pathways in bacteria for hydrogen production and the enzymes involved in various thermophilic hydrogen producing pathways in microorganisms. It also focuses on the current status of thermophilic biohydrogen production through fermentation of commercially viable substrates, such as agricultural residues. The use of metabolic engineering to attain certain physiological desirable characteristics in H₂‐producing microorganisms, culture conditions, and types of bioreactors to be used are reviewed. Major obstacles in industrial production of biohydrogen like low volumetric hydrogen production and its environmental impact are identified. The review has further identified current limitations in the commercial thermophilic hydrogen production and suggested methods like the use of heat exchangers and effluent recirculation to reduce the production cost. Copyright © 2015 John Wiley & Sons, Ltd.