Assessment of the in situ biomethanation potential of a deep aquifer used for natural gas storage.

The dihydrogen (H2) sector is undergoing development and will require massive storage solutions. To minimize costs, the conversion of underground geological storage sites, such as deep aquifers, used for natural gas storage into future underground hydrogen storage sites is the favored scenario. However, these sites contain microorganisms capable of consuming H2, mainly sulfate reducers and methanogens. Methanogenesis is, therefore expected but its intensity must be evaluated. Here, in a deep aquifer used for underground geological storage, 17 sites were sampled, with low sulfate concentrations ranging from 21.9 to 197.8 µM and a slow renewal of formation water. H2-selected communities mainly were composed of the families Methanobacteriaceae and Methanothermobacteriaceae and the genera Desulfovibrio, Thermodesulfovibrio, and Desulforamulus. Experiments were done under different conditions, and sulfate reduction, as well as methanogenesis, were demonstrated in the presence of a H2 or H2/CO2 (80/20) gas phase, with or without calcite/site rock. These metabolisms led to an increase in pH up to 10.2 under certain conditions (without CO2). The results suggest competition for CO2 between lithoautotrophs and carbonate mineral precipitation, which could limit microbial H2 consumption.

Recent updates in biohydrogen production strategies and life-cycle assessment for sustainable future.

Biohydrogen (bio-H2) is regarded as a clean, non-toxic, energy carrier and has enormous potential for transforming fossil fuel-based economy. The development of a continuous high-rate H2 production with low-cost economics following an environmentally friendly approach should be admired for technology demonstration. Thus, the current review discusses the biotechnological and thermochemical pathways for H2 production. Thermochemical conversion involves pyrolysis and gasification routes, while biotechnological involves light-dependent processes (e.g., direct and indirect photolysis, photo/ dark fermentation strategies). Moreover, environmentally friendly technologies can be created while utilizing renewable energy sources including lignocellulosic, wastewater, sludge, microalgae, and others, which are still being developed. Lifecycle assessment (LCA) evaluates and integrates the economic, environmental, and social performance of H2 production from biomass, microalgae, and biochar. Moreover, system boundaries evaluation, i.e., global warming potential, acidification, eutrophication, and sensitivity analysis could lead in development of sustainable bioenergy transition with high economic and environmental benefits.

Factor-based assessment of continuous bio-H2 production from cheese whey.

Despite having been widely investigated, dark fermentative H2 production from organic residues is still limited by process-related issues which may hamper the perspectives of full-scale process implementation. Such constraints are mainly due to the process complexity, which is largely affected by multiple and often mutually interacting factors. In the present work, the results of continuous fermentative H2 production experiments using synthetic cheese whey as the input substrate were used to gain detailed knowledge of the process features and identify suitable and critical operating conditions. Specifically, innovative process interpretation involved a combination of analytical characterization of the fermentation broth, mass balance calculations and statistical methods (correlation and principal component analyses) to derive systematic considerations for process characterization and scale-up. The metabolic products mainly included acetate and butyrate, which however were likely to derive (in different proportions depending on the operating conditions) from both hydrogenogenic and competing pathways. For some tests, lactate and succinate were also found to have been formed. It was observed that the main features of the process (H2 yield and rate, stability condition) were correlated with the operational and analytical parameters. The first three principal components identified by the statistical analysis were able to account for: 1) the effect of retention time and total metabolites produced; 2) biogas (H2 and CO2) generation, butyrate production and stability condition; and 3) organic loading rate and propionate production. The results suggested that the main features of hydrogenogenic fermentation can be described by a reduced set of factors that may be usefully adopted for both process monitoring and prediction purposes.

[Assessment of the state of the small intestine microbiota in children on a long-term dairy-free diet].

An overview of recent outcomes of studies indicates an imbalance in the diet of children. Quantitative and qualitative malnutrition of children is the basis of a number of childhood diseases. The aim of the research was to study the prevalence of small intestine bacterial overgrowth syndrome (SIBO) in children on a long-term dairy-free diet. Material and methods. 40 children aged 7-11 years following a long-term dairy-free diet (average 3 years and 5 months, from 0.5 to 6.3 years) were examined (main group). 30 children who did not follow restrictive diets were consisted control group. In all children, SIBO was determined using a hydrogen breath test with a load of lactulose using a digital analyzer of exhaled hydrogen. Results. The proportion of children with intolerance to dairy products was 32.5%: 10.0% with allergy to cow's milk proteins, and 22.5% with lactose intolerance. 27.5% children followed a dairy-free diet according to an unjustified prescription by physician. 30.0% of children did not consume dairy products because of their unwillingness. 10.0% of children did not consume dairy products due to the unwillingness of their parents. An imbalance in the microbiota of the small intestine during the hydrogen breath test with lactulose loading was detected in 55.0% of children following a long-term dairy-free diet. 22.5% of children complained of recurrent abdominal pain, diarrhea was determined in 10.0%, constipation - in 7.5%, nausea - in 10.0%. In the control group, the SIBO during the hydrogen breath test with lactulose loading was found in 20.0%. Periodic abdominal pain was determined in 10.0%, nausea - in 6.7%, diarrhea - in 10.0%, constipation - in 3.3% children. Conclusion. Thus, among children of primary school age who follow a long-term dairyfree diet, SIBO is significantly more often recorded relative to children who are on a traditional type of diet.

A high-performance capillary-fed electrolysis cell promises more cost-competitive renewable hydrogen.

Renewable, or green, hydrogen will play a critical role in the decarbonisation of hard-to-abate sectors and will therefore be important in limiting global warming. However, renewable hydrogen is not cost-competitive with fossil fuels, due to the moderate energy efficiency and high capital costs of traditional water electrolysers. Here a unique concept of water electrolysis is introduced, wherein water is supplied to hydrogen- and oxygen-evolving electrodes via capillary-induced transport along a porous inter-electrode separator, leading to inherently bubble-free operation at the electrodes. An alkaline capillary-fed electrolysis cell of this type demonstrates water electrolysis performance exceeding commercial electrolysis cells, with a cell voltage at 0.5 A cm-2 and 85 °C of only 1.51 V, equating to 98% energy efficiency, with an energy consumption of 40.4 kWh/kg hydrogen (vs. ~47.5 kWh/kg in commercial electrolysis cells). High energy efficiency, combined with the promise of a simplified balance-of-plant, brings cost-competitive renewable hydrogen closer to reality.

Microbial hydrogen economy alleviates colitis by reprogramming colonocyte metabolism and reinforcing intestinal barrier.

With the rapid development and high therapeutic efficiency and biosafety of gas-involving theranostics, hydrogen medicine has been particularly outstanding because hydrogen gas (H2), a microbial-derived gas, has potent anti-oxidative, anti-apoptotic, and anti-inflammatory activities in many disease models. Studies have suggested that H2-enriched saline/water alleviates colitis in murine models; however, the underlying mechanism remains poorly understood. Despite evidence demonstrating the importance of the microbial hydrogen economy, which reflects the balance between H2-producing (hydrogenogenic) and H2-utilizing (hydrogenotrophic) microbes in maintaining colonic mucosal ecosystems, minimal efforts have been exerted to manipulate relevant H2-microbe interactions for colonic health. Consistent with previous studies, we found that administration of hydrogen-rich saline (HS) ameliorated dextran sulfate sodium-induced acute colitis in a mouse model. Furthermore, we demonstrated that HS administration can increase the abundance of intestinal-specific short-chain fatty acid (SCFA)-producing bacteria and SCFA production, thereby activating the intracellular butyrate sensor peroxisome proliferator-activated receptor γ signaling and decreasing the epithelial expression of Nos2, consequently promoting the recovery of the colonic anaerobic environment. Our results also indicated that HS administration ameliorated disrupted intestinal barrier functions by modulating specific mucosa-associated mucolytic bacteria, leading to substantial inhibition of opportunistic pathogenic Escherichia coli expansion as well as a significant increase in the expression of interepithelial tight junction proteins and a decrease in intestinal barrier permeability in mice with colitis. Exogenous H2 reprograms colonocyte metabolism by regulating the H2-gut microbiota-SCFAs axis and strengthens the intestinal barrier by modulating specific mucosa-associated mucolytic bacteria, wherein improved microbial hydrogen economy alleviates colitis.

Utilization of Agave durangensis leaves by Bacillus cereus 4N for polyhydroxybutyrate (PHB) biosynthesis.

Lignocellulosic wastes may provide a means to economize polyhydroxybutyrate (PHB) production. This study has proposed the use of Agave durangensis leaves obtained from the artisanal mezcal industry as a novel substrate for this aim. Results revealed an increase in PHB biosynthesis (0.32 g/L) and improvement in %PHB (16.79-19.51%) by Bacillus cereus 4N when A. durangensis leaves used as carbon source were physically pre-treated by ultrasound for 30 min (ADL + US30') and thermally pre-treated (ADL + Q). Chemical analyses and SEM studies revealed compositional and morphological changes when A. durangensis leaves were physically pre-treated. Also, elemental analysis of growth media showed that carbon/nitrogen ratios of 14-21, and low nitrogen, hydrogen, and protein content were well-suited for PHB biosynthesis. Confocal microscopy revealed morphological changes in the bacterial cell and carbonosome structure under the influence of different substrates. Finally, Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) analyses showed that homopolymeric PHB with a high thermal-resistance (271.94-272.89 °C) was produced. Therefore, the present study demonstrates the potential use of physically pre-treated A. durangensis leaves to produce PHB. These results promote the development of a circular economy in Mexico, where lignocellulosic wastes can be employed to produce value-added biotechnological products.

Effects of operating conditions on biogas production in an anaerobic digestion system of the food and beverage industry.

BACKGROUND: Food residuals (FR) were anaerobically biotransformed to produce biogases (e.g. methane and hydrogen), and different pre-treatment conditions, including particle size, oil content, pH and salt content, were controlled in this study. The bio-solids of a municipal solid waste (MSW) from a wastewater treatment plant were added to assess its effect on anaerobic transformation efficiency and gas yields. RESULTS: The breaking of FR and the application of MSW were effective in enhancing the transformation efficiency and yield of biogases. The energy transfer efficiency value of the combined FRs used in this study was probably 23%. However, it can be very cost effective to apply arbitrary proportions to treat two types of FR in the anaerobic digestion tank of a wastewater treatment plant. It was also found that the alkalinity and pH value were two major parameters that controlled the success of the transformation. About 0.16-0.17 kg of alkalinity was needed during the anaerobic digestion of 1 kg dry FR, but this requirement was decreased by the treatment applying MSW. Olive oil had higher reducing rates when used as a substitute for heat-oxidized oil to study the effect of oil content on methylation. CONCLUSION: The conditions for anaerobic digestion established in this study were practical for the digestion of FR in wastewater treatment plants in Taiwan. However, we nonetheless found that it was cost effective to use arbitrary proportions for both types of FR and integrate the anaerobic digestion process used in wastewater treatment plants. © 2020 Society of Chemical Industry.

In vitro assessment of prebiotic properties of xylooligosaccharides produced by Bacillus subtilis 3610.

Xylooligosaccharides (XOS) are emergent prebiotics exhibiting high potential as food ingredients. In this work, in vitro studies were performed using human fecal inocula from two healthy donors (D 1 and D2) to evaluate the prebiotic effect of commercial lactulose and XOS produced in a single-step by recombinant Bacillus subtilis 3610. The fermentation of lactulose led to the highest production of lactate (D1: 33.7 ±â€¯0.5 mM; D2:19.7 ±â€¯0.3 mM) and acetate (D1: 77.5 ±â€¯0.6 mM; D2: 81.0 ±â€¯0.7 mM), while XOS led to the highest production of butyrate (D1: 9.0 ±â€¯0.6 mM; D2: 10.5 ±â€¯0.8 mM) and CO2 (D1: 8.92 ±â€¯0.02 mM; D2: 11.4 ±â€¯0.3 mM). Microbiota analysis showed a significant decrease in the relative abundance of Proteobacteria for both substrates and an increase in Bifidobacterium and Lactobacillus for lactulose, and Bacteroides for XOS.

Biohythane production of post-hydrothermal liquefaction wastewater: A comparison of two-stage fermentation and catalytic hydrothermal gasification.

Developing efficient methods to recover energy from post-hydrothermal liquefaction wastewater (PHW) is critical for scaling up hydrothermal liquefaction (HTL) technology. Here we evaluated two-stage fermentation (TF) and catalytic hydrothermal gasification (CHG) for biohythane production using PHW. A hydrogen yield of 29 mL·g-1 COD and methane yield of 254 mL·g-1 COD were achieved via TF. In comparison, a higher hydrogen yield (116 mL·g-1 COD) and lower methane yield (65 mL·g-1 COD) were achieved during CHG. Further, a techno-economic and sensitivity analysis was conducted. The capital cost and operating cost for TF varied with the different reactor systems. TF with high-rate reactors suggested its promising commercialized application as it had a lower minimum selling price (-0.71 to 2.59 USD per gallon of gasoline equivalent) compared with conventional fossil fuels under both the best and reference market conditions. Compared with TF, CHG was only likely to be profitable under the best case conditions.

Fermentative hydrogen production from low-value substrates.

Hydrogen is a promising energy source that is believed to replace the conventional energy sources e.g. fossil fuels over years. Hydrogen production methods can be divided into conventional production methods which depend mainly on fossil fuels and alternative production methods including electrolysis of water, biophotolysis and fermentation hydrogen production from organic waste materials. Compared to the conventional methods, the alternative hydrogen production methods are less energy intensive and negative-value substrates i.e. waste materials can be used to produce hydrogen. Among the alternative methods, fermentation process including dark and photo-fermentation has gained more attention because these processes are simple, waste materials can be utilized, and high hydrogen yields can be achieved. The fermentation process is affected by several parameters such as type of inoculum, pH, temperature, substrate type and concentration, hydraulic retention time, etc. In order to achieve optimum hydrogen yields and maximum substrate degradation, the operating conditions of the fermentation process must be optimized. In this review, two routes for biohydrogen production as dark and photo-fermentation are discussed. Dark/photo-fermentation technology is a new approach that can be used to increase the hydrogen yield and improve the energy recovery from organic wastes.

Exfoliated molybdenum di-sulfide (MoS2) electrode for hydrogen production in microbial electrolysis cell.

The most widely reported catalyst in microbial electrochemical cells (MEC) cathodes is platinum (Pt). The disadvantages of Pt include its high cost and sensitivity to various molecules. In this research an exfoliated molybdenum di-sulfide (MoS2-EF) catalyst was synthesized. The size of the obtained particles was 200 ±â€¯50 nm, 50-fold smaller than the pristine MoS2 catalyst. The MoS2-EF Raman spectrum displays the E12g and A1g peaks at 373 cm-1 and 399 cm-1. Electrochemical characterization by linear sweep voltammetry (LSV) of a rotating disc electrode RDE showed that the current density of Pt in 0.5 M H2SO4 was 3.3 times higher than MoS2-EF. However, in phosphate buffer (pH-7) electrolyte this ratio diminished to 1.9. The polarization curve of Pt, MoS2-EF and the pristine MoS2 electrodes, at -1.3 V in MEC configuration in abiotic conditions exhibit current densities of 17.46, 12.67 and 3.09 mA cm-2, respectively. Hydrogen evolution rates in the same MEC with a Geobacter sulfurreducens anode and Pt, MoS2-EF and the pristine MoS2 cathodes were 0.106, 0.133 and 0.083 m3 d-1 m-3, respectively. The results in this study show that MoS2-EF led to highly purified hydrogen and that this catalyst can serve as an electrochemical active and cost-effective alternative to Pt.

Enhancement of fermentative hydrogen production from Spirogyra sp. by increased carbohydrate accumulation and selection of the biomass pretreatment under a biorefinery model.

In this work, hydrogen (H2) was produced through the fermentation of Spirogyra sp. biomass by Clostridium butyricum DSM 10702. Macronutrient stress was applied to increase the carbohydrate content in Spirogyra, and a 36% (w/w) accumulation of carbohydrates was reached by nitrogen depletion. The use of wet microalga as fermentable substrate was compared with physically and chemically treated biomass for increased carbohydrate solubilisation. The combination of drying, bead beating and mild acid hydrolysis produced a saccharification yield of 90.3% (w/w). The H2 production from Spirogyra hydrolysate was 3.9 L H2 L-1, equivalent to 146.3 mL H2 g-1 microalga dry weight. The presence of protein (23.2 ± 0.3% w/w) and valuable pigments, such as astaxanthin (38.8% of the total pigment content), makes this microalga suitable to be used simultaneously in both food and feed applications. In a Spirogyra based biorefinery, the potential energy production and food-grade protein and pigments revenue per cubic meter of microalga culture per year was estimated on 7.4 MJ, US $412 and US $15, respectively, thereby contributing to the cost efficiency and sustainability of the whole bioconversion process.

Multi-parametric rigid and flexible, low-cost, disposable sensing platforms for biomedical applications.

The measurement of Na+, K+ and H+ is essential in medicine and plays an important role in the assessment of tissue ischemia. Microfabrication, inkjet- and screen-printing can be used for solid contact ion selective electrodes (ISE) realization; these, however, can be non-standardized, costly and time consuming processes. We present the realization of ISEs on post-processed electrodes fabricated via standardized printed circuit board (PCB) manufacturing techniques. In vitro results are presented from two rigid platforms (32 ISEs) for liquid sample dip-stick measurements and two flexible platforms (6 and 32 ISEs) for post-surgical intestinal tissue monitoring, each with a common reference electrode (RE). These are combined with optimized tetrapolar bioimpedance sensors for tissue ischemia detection. Both electroless and hard gold PCB finishes are examined. Apart from the electroless rigid platform, the rest demonstrated comparable and superior performance, with the pH sensors demonstrating the greatest deviation; the flexible hard gold platform achieved a sensitivity 4.6mV/pH and 49.2mV/pH greater than the electroless flexible and rigid platforms, respectively. The best overall performance was achieved with the hard gold flexible platform with sensitivities as large as 73.4mV/pH, 56.3mV/log [Na+], and 57.4mV/log [K+] vs. custom REs on the same substrate. Simultaneous measurement of target analytes is demonstrated with test solutions and saliva samples. The results demonstrate superior performance to other PCB-based pH sensors and Na+ and K+ PCB-based sensors with comparable performance to potentiometric sensors fabricated with other techniques, paving the way towards mass-produced, low-cost, disposable, multi-parametric chemical sensing diagnostic platforms.

Microalgal hydrogen production: prospects of an essential technology for a clean and sustainable energy economy.

Modern energy production is required to undergo a dramatic transformation. It will have to replace fossil fuel use by a sustainable and clean energy economy while meeting the growing world energy needs. This review analyzes the current energy sector, available energy sources, and energy conversion technologies. Solar energy is the only energy source with the potential to fully replace fossil fuels, and hydrogen is a crucial energy carrier for ensuring energy availability across the globe. The importance of photosynthetic hydrogen production for a solar-powered hydrogen economy is highlighted and the development and potential of this technology are discussed. Much successful research for improved photosynthetic hydrogen production under laboratory conditions has been reported, and attempts are underway to develop upscale systems. We suggest that a process of integrating these achievements into one system to strive for efficient sustainable energy conversion is already justified. Pursuing this goal may lead to a mature technology for industrial deployment.

Assessment of active methanogenic archaea in a methanol-fed upflow anaerobic sludge blanket reactor.

Methanogenic archaea enrichment of a granular sludge was undertaken in an upflow anaerobic sludge blanket (UASB) reactor fed with methanol in order to enrich methylotrophic and hydrogenotrophic methanogenic populations. A microbial community assessment, in terms of microbial composition and activity-throughout the different stages of the feeding process with methanol and acetate-was performed using specific methanogenic activity (SMA) assays, quantitative real-time polymerase chain reaction (qPCR), and high-throughput sequencing of 16S ribosomal RNA (rRNA) genes from DNA and complementary DNA (cDNA). Distinct methanogenic enrichment was revealed by qPCR of mcrA gene in the methanol-fed community, being two orders of magnitude higher with respect to the initial inoculum, achieving a final mcrA/16S rRNA ratio of 0.25. High-throughput sequencing analysis revealed that the resulting methanogenic population was mainly composed by methylotrophic archaea (Methanomethylovorans and Methanolobus genus), being also highly active according to the RNA-based assessment. SMA confirmed that the methylotrophic pathway, with a direct conversion of methanol to CH4, was the main step of methanol degradation in the UASB. The biomass from the UASB, enriched in methanogenic archaea, may bear great potential as additional inoculum for bioreactors to carry out biogas production and other related processes.

Biohydrogen production from waste bread in a continuous stirred tank reactor: A techno-economic analysis.

Biohydrogen production from waste bread in a continuous stirred tank reactor (CSTR) was techno-economically assessed. The treating capacity of the H2-producing plant was assumed to be 2 ton waste bread per day with lifetime of 10years. Aspen Plus was used to simulate the mass and energy balance of the plant. The total capital investment (TCI), total annual production cost (TAPC) and annual revenue of the plant were USD931020, USD299746/year and USD639920/year, respectively. The unit hydrogen production cost was USD1.34/m3 H2 (or USD14.89/kg H2). The payback period and net present value (NPV) of the plant were 4.8years and USD1266654, respectively. Hydrogen price and operators cost were the most important variables on the NPV. It was concluded that biohydrogen production from waste bread in the CSTR was feasible for practical application.

Biomanufacture of nano-Pd(0) by Escherichia coli and electrochemical activity of bio-Pd(0) made at the expense of H2 and formate as electron donors.

OBJECTIVE: Palladised cells of Desulfovibrio desulfuricans and Shewanella oneidensis have been reported as fuel cell electrocatalysts but growth at scale may be unattractive/costly; we have evaluated the potential of using E. coli, using H2/formate for Pd-nanoparticle manufacture. RESULTS: Using 'bio-Pd' made under H2 (20 wt%) cyclic voltammograms suggested electrochemical activity of bio-NPs in a native state, attributed to proton adsorption/desorption. Bio-Pd prepared using formate as the electron donor gave smaller, well separated NPs; this material showed no electrochemical properties, and hence little potential for fuel cell use using a simple preparation technique. Bio-Pd on S. oneidensis gave similar results to those obtained using E. coli. CONCLUSION: Bio-Pd is sufficiently conductive to make an E. coli-derived electrochemically active material on intact, unprocessed bacterial cells if prepared at the expense of H2, showing potential for fuel cell applications using a simple one-step preparation method.