Investigating the activity of indigenous microbial communities from Italian depleted gas reservoirs and their possible impact on underground hydrogen storage

H2 produced from renewable energies will play a central role in both greenhouse gas reduction and decarbonization by 2050. Nonetheless, to improve H2 diffusion and utilization as a fuel, large storage capacity systems are needed. Underground storage of natural gas in depleted reservoirs, aquifers and salt caverns is a well-established technology. However, new challenges arise when it comes to storing hydrogen due to the occurrence and activity of indigenous microbial populations in deep geological formations. In a previous study, four Italian natural gas reservoirs were characterized both from a hydro-chemical and microbiological point of view, and predictive functional analyses were carried out with the perspective of underground hydrogen storage (UHS). In the present work, formation waters from the same reservoirs were used as inoculant during batch cultivation tests to characterize microbial activity and its effects on different gas mixtures. Results evidence a predominant acidogenic/acetogenic activity, whilst methanogenic and sulfate reducing activity were only marginal for all tested inoculants. Furthermore, the microbial activation of tested samples is strongly influenced by nutrient availability. Obtained results were fitted and screened in a computational model which would allow deep insights in the study of microbial activity in the context of UHS.

Biogeochemical characterization of four depleted gas reservoirs for conversion into underground hydrogen storage

Depleted gas reservoirs are a valuable option for underground hydrogen storage (UHS). However, different classes of microorganisms, which are capable of using free H2 as a reducing agent for their metabolism, inhabit deep underground formations and can potentially affect the storage. This study integrates metagenomics based on Illumina-NGS sequencing of bacterial and archaeal 16S rRNA and dsrB and mcrA functional genes to unveil the composition and the variability of indigenous microbial populations of four Italian depleted reservoirs. The obtained mcrA sequences allow us to implement the existing taxonomic database for mcrA gene sequences with newly classified sequences obtained from the Italian gas reservoirs. Moreover, the KEGG and COG predictive functional annotation was used to highlight the metabolic pathways potentially associated with hydrogenotrophic metabolisms. The analyses revealed the specificity of each reservoir microbial community, and taxonomic and functional data highlighted the presence of an enriched number of taxa, whose activity depends on both reservoir hydrochemical composition and nutrient availability, of potential relevance in the context of UHS. This study is the very first to address the profiling of the microbial population and allowed us to perform a preliminary assessment of UHS feasibility in Italy.

Expanding the product portfolio of carbon dioxide and hydrogen-based gas fermentation with an evolved strain of Clostridium carboxidivorans

CO2:H2-based gas fermentation with acetogenic Clostridium species are at an early stage of development. This work exploited the Adaptive Laboratory Evolution technique to improve the growth of C. carboxidivorans P7 on CO2 and H2. An adapted strain with decreased growth lag phase and improved biomass production was obtained. Genomic analysis revealed a conserved frameshift mutation in the catalytic subunit of the hexameric hydrogenase gene. The resulted truncated protein variant, most likely lacking its functionality, suggests that other hydrogenases might be more efficient for H2-based growth of this strain. Furthermore, the adapted strain generated hexanol as primary fermentation product. For the first time, hexanol was produced directly from CO2:H2 blend, achieving the highest maximum productivity reported so far via gas fermentation. Traces of valerate, pentanol, eptanol and octanol were observed in the fermentation broth. The adapted strain shows promising to enrich the product spectrum targetable by future gas fermentation processes.

Perspective on the use of methanogens in lithium recovery from brines

Methanogenic archaea stand out as multipurpose biocatalysts for different applications in wide-ranging industrial sectors due to their crucial role in the methane (CH4) cycle and ubiquity in natural environments. The increasing demand for raw materials required by the manufacturing sector (i.e., metals-, concrete-, chemicals-, plastic- and lubricants-based industries) represents a milestone for the global economy and one of the main sources of CO2 emissions. Recovery of critical raw materials (CRMs) from byproducts generated along their supply chain, rather than massive mining operations for mineral extraction and metal smelting, represents a sustainable choice. Demand for lithium (Li), included among CRMs in 2023, grew by 17.1% in the last decades, mostly due to its application in rechargeable lithium-ion batteries. In addition to mineral deposits, the natural resources of Li comprise water, ranging from low Li concentrations (seawater and freshwater) to higher ones (salt lakes and artificial brines). Brines from water desalination can be high in Li content which can be recovered. However, biological brine treatment is not a popular methodology. The methanogenic community has already demonstrated its ability to recover several CRMs which are not essential to their metabolism. Here, we attempt to interconnect the well-established biomethanation process with Li recovery from brines, by analyzing the methanogenic species which may be suitable to grow in brine-like environments and the corresponding mechanism of recovery. Moreover, key factors which should be considered to establish the techno-economic feasibility of this process are here discussed.

Design, Fabrication, and Experimental Validation of Microfluidic Devices for the Investigation of Pore-Scale Phenomena in Underground Gas Storage Systems

The understanding of multiphase flow phenomena occurring in porous media at the pore scale is fundamental in a significant number of fields, from life science to geo and environmental engineering. However, because of the optical opacity and the geometrical complexity of natural porous media, detailed visual characterization is not possible or is limited and requires powerful and expensive imaging techniques. As a consequence, the understanding of micro-scale behavior is based on the interpretation of macro-scale parameters and indirect measurements. Microfluidic devices are transparent and synthetic tools that reproduce the porous network on a 2D plane, enabling the direct visualization of the fluid dynamics. Moreover, microfluidic patterns (also called micromodels) can be specifically designed according to research interests by tuning their geometrical features and surface properties. In this work we design, fabricate and test two different micromodels for the visualization and analysis of the gas-brine fluid flow, occurring during gas injection and withdrawal in underground storage systems. In particular, we compare two different designs: a regular grid and a real rock-like pattern reconstructed from a thin section of a sample of Hostun rock. We characterize the two media in terms of porosity, tortuosity and pore size distribution using the A* algorithm and CFD simulation. We fabricate PDMS-glass devices via soft lithography, and we perform preliminary air-water displacement tests at different capillary numbers to observe the impact of the design on the fluid dynamics. This preliminary work serves as a validation of design and fabrication procedures and opens the way to further investigations.

P239 TOLERABILITY OF SACUBITRIL/VALSARTAN TREATMENT IN OLDER PATIENTS WITH HEART FAILURE WITH REDUCED EJECTION FRACTION: PRELIMINARY DATA FROM THE REAL–WORLD AGING–HF REGISTRY

Background

Although older patients with heart failure (HF) with reduced ejection fraction enrolled in PARADIGM–HF showed a good tolerance to sacubitril/valsartan (Sa/Va), more real–word data are needed to define their tolerability in this population. Aim: To describe the Sa/Va tolerability and titration in older HFrEF patients followed by our HF outpatient.

Methods

HFrEF patients aged ≥65 years and treated with Sa/Va from November 2016 to June 2021 were enrolled, assessing Sa/Va tolerability at six months and its clinical and hemodynamic effects.

Results

We enrolled 101 patients with a mean age of 78 years (⁓20% female). The aetiology was ischemic in 59% of cases while the mean ejection fraction was 31%. Sa/Va was prescribed at the starting dose (24/26mg) and intermediate dose (49/51mg) in 91% and 9% of cases, respectively. After six months, 9 of the 100 patients still alive had discontinued treatment with Sa/Va (4 for symptomatic hypotension, 3 for suspected allergic reaction and 2 for worsening renal function). Of the 91 patients still on therapy, only 17 had reached the target dose (97/103mg) while 28 were at the intermediate dose (Figure 1). Symptomatic hypotension (62%), hyperkalaemia (15%) and worsening of renal function (4%) were the main causes of maintaining Sa/Va therapy at the starting dose; note, in 15% of cases a specific cause of non–titration was not identified. Comparing HF treatment between starting dose vs higher–dose patients, after six months in low–dose patients there was a slight improvement in mineralcorticosteroid receptor antagonist (MRA) prescription and in combination therapy (Sa/Va, beta–blocker and MRA) while in patients at higher–doses there was a significant decrease (Figure 2). In patients still receiving Sa/Va, significant clinical improvement was observed while renal function, K+ levels and systolic blood pressure remained stable (Figure 3).

Conclusions

After six months of treatment, Sa/Va was well tolerated in most of our older patients and used in combination with a beta–blocker and an MRA in a high percentage of cases, although a reduction in MRA prescription is observed in patients taking higher dosages of Sa/Va. In addition, there was a marked improvement in the clinical variables.

P252 PROTOCOL FOR TELEHEALTH MANAGEMENT AND STRATIFICATION RISK OF ELDERLY PATIENTS WITH CHRONIC HEART FAILURE DURING THE COVID–19 PANDEMIC: A MID–TERM PROGNOSTIC EVALUTATION BY TELEHFCOVID–19 SCORE

Introduction

The Coronavirus Disease (COVID–19) pandemic and its consequences has forced physicians to develop telematic methods in order to follow up patients with cronic diseases, such as heart failure (HF).

Objectives

To evaluate TeleHFCovid–19 score as a mid–term (six months) prognostic score in terms of prediction of hospitalitazion and cardiovascular mortality in patients with chronic HF during Covid–19 pandemic.

Methods

During COVID–19 pandemic (from March 2020 to May 2020), we were forced to cancel nearly all follow–up checks in our HF outpatient clinic. We hence standardized a telephone follow–up by developing a questionnaire (Fig. 1) from which we then obtained a score, later called the “TeleHFCovid–19 score” (0–29). This score stratified patients in three risk score groups: green (0–3), yellow (4–8), and red (≥9), for which the next telefonic evaluation was planned after 4, 2 and 1 weeks, respectively.

Results

146 patients were enrolled: 112 were classified as green, 21 as yellow and 13 as red. Mean age was 81 years, females were 40%. Approximately one third had EF < 40%. At six months, compared to red (69.2%) and yellow patients (33.3%), green patients (8.9%) presented a significantly lower rate of the composite outcome of cardiovascular death and/or HF hospitalization, (p < 0.001, Fig 2). Multivariate analysis showed that high levels of creatinine (OR 5.960, 95% CI 1.627–21.837, p = 0.007), dyspnea at rest or for basic activities (OR 2.469, 95% CI 1.216–5.013, p = 0.012) and a high loop–diuretic dosage (OR 6.224, 95% CI 1.504–25.753, p = 0.012) were indipendently associated with the outcome. Moreover, ROC analysis showed a high sensibility and specificity for our score at six months (AUC =0.789, 95% CI 0.682–0.896, p < 0.001), with a score < 4.5 (very close to the green group cut–off) that identified lower–risk subjects (Fig 3).

Conclusions

The TeleHFCovid–19 score was able to correctly identify patients with good outcomes at six months. Furthermore, it has the ability to stratify the adverse event risk and this could represent a useful tool to appropriately schedule the reevaluation timing of these patients and to identify those who may need urgent hospital evaluation.

P250 PROTOCOL FOR TELEHEALTH EVALUATION AND FOLLOW–UP OF PATIENTS WITH CHRONIC HEART FAILURE DURING THE COVID–19 PANDEMIC

Background

After the lockdown imposed by the COVID19 pandemic, physicians had to limite ambulatory visits to exceptional cases to reduce interpersonal contact. We structured a telephone follow–up developing a standardized 23 item questionnaire to administrate to our HF outpatient clinic and from whom we obtained the Covid–19–HFscore.

Methods

The patients were identified by a numeric code, date of birth and gender. The questionnaire was designed for rapid administration during telephone interview (on average 6 minutes) and was administered directly by physicians to patients and/or to their caregiver. It was built to reproduce our usual clinical evaluation.

Results

As shown in Figure 1, we investigated seven domains: 1) social and functional condition 2) mood 3) adherence to pharmacological and non–pharmacological recommendations (blood pressure, heart rate, weight monitoring and fluid intake control) 4) clinical and hemodynamic status 5) recording of laboratory tests 6) current pharmacological treatment 7) recent evaluation by family physician or need to contact emergency services followed or not by hospitalisation. General and pharmacological recommendations as well as the following telephone contact were finally recorded. To determine the timing of the next telephonic evaluation, we decided to weight questions regarding clinical and hemodynamic status, adherence to pharmacological and non–pharmacological recommendations, therapeutic changes and need for hospitalisation by scoring the answers (from 1 to 3) to build a score. The sum of individual scores represented the novel TeleHFCovid19–score, ranging from 0 to 29. Based on such score, three groups of patients were identified by arbitrary cut–off levels: the green (score <4), the yellow (score 4–8) and the red (score ≥9) group, for which next telephonic evaluation was planned respectively after four, two and one week respectively. Alternatively, the red group could receive recommendation for urgent hospital evaluation.

Conclusion

During this emergency situation this questionnaire could be a useful clinical tool to help physicians maintaining a regular FU of their patients and identifying patients at greatest risk of imminent instability. Furthermore, this instrument could also represent a useful resource in the management of low–risk HF patients.

P260 PRELIMINARY EXPERIENCE OF REPEATED LEVOSIMENDAN INFUSIONS IN ELDERLY OUTPATIENTS WITH ADVANCED HEART FAILURE

Background

The use of intermittent infusion of Levosimendan (L) demonstrated to be able to reduce hospitalisations and to improve functional capacity and quality of life in patients with advanced heart failure (HF).

Purpose

To describe our preliminary experience regarding L intermittent infusions in advanced HF older outpatients.

Methods

A maximum of three consecutive L infusions were carried out 14 days apart. The duration of each session was 8 hours. The starting infusion rate was 0.05 μg/Kg/min, titrated every 30/60‘ up to a maximum of 0.2 μg/Kg/min based on blood pressure, heart rate and arrhythmias recorded during telemetry. We evaluated patients by clinical, laboratory and echocardiographic controls at baseline and two weeks after the end of treatment.

Results

Since November 2020 we enrolled 17 patients with a mean age of 77 years; 12% were women. HF etiology was ischemic in 64% of cases and the mean ejection fraction was 30%. A total of 41 infusions were performed, the mean dose of L administered was 5.4 mg/infusion. Three patients did not complete the expected treatment, one due to an intercurrent COVID–19 infection and two because of social issues. In 28 sessions the maximum infusion rate was reached, while in 12 a lower rate; in one case drug infusion was suspended (Figure 1). The main complication observed was marked non–symptomatic hypotension, followed by the onset of atrial fibrillation or frequently ventricular extrasystole. As shown in Figure 2, at the end of the infusion cycles, there was an improvement of clinical and hemodynamic parameters. Moreover, at the end of the infusion cycles, we observed a reduction in the mean dose of loop diuretic prescribed and an increase in the prescription of disease–modify treatment, according to HF guidelines (Figure 3).

Conclusions

In our preliminary experience repeated infusions of L appear to be well tolerated in older patients with advanced HF. Although there was an improvement in congestion parameters and targeted therapy for HF, more data will be needed in the future to confirm its safety and efficacy, also in terms of guidelines–directed medical therapy.

Geological surface reconstruction from 3D point clouds

The numerical simulation of phenomena such as subsurface fluid flow or rock deformations are based on geological models, where volumes are typically defined through stratigraphic surfaces and faults, which constitute the geometric constraints, and then discretized into blocks to which relevant petrophysical or stress-strain properties are assigned.

This paper illustrates the process by which it is possible to reconstruct the triangulation of 3D geological surfaces assigned as point clouds. These geological surfaces can then be used in codes dedicated to volume discretization to generate models of underground rocks.

The method comprises the following:

- Characterization of the best fitting plane and identification of the concave hull of the point cloud which is projected on it

- Triangulation of the point cloud on the plane, constrained to the Planar Straight Line Graph constituted by the concave hull

The algorithm, implemented in C++, depends exclusively on two parameters (nDig, maxCut) which allow one to easily evaluate the optimal refinement level of the hull on a case by case basis.

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine: Brussels, Belgium. 15-18 March 2016

[This corrects the article DOI: 10.1186/s13054-016-1208-6.].

How to Approach Subsidence Evaluation for Marginal Fields: A Case History

This paper presents the evaluation of the subsidence potentially induced by underground storage of natural gas in a marginal depleted field located in Southern Italy. The critical aspect of the study was the lack of data because economic and logistic reasons had restricted data acquisition at the regional scale to perform a geomechanical study. This limitation was overcome by accurately gathering the available data from public sources so that the geometry of a largescale 3D model could be defined and the formations properly characterized for rock deformation analysis. Well logs, seismic data and subsidence surveys at the regional scale, available in open databases and in the technical literature, were integrated with the available geological and fluid-flow information at the reservoir scale. First of all, a 3D geological model, at the regional scale, incorporating the existing model of the reservoir was developed to describe the key features of a large subsurface volume while preserving the detail of the storage reservoir. Then, a regional geomechanical model was set up for coupled mechanic and fluid-flow analyses. The stress and strain evolution and the associated subsidence induced in the reservoir and surrounding formations by historical primary production as well as future gas storage activities were investigated. Eventually, the obtained results were validated against the measurements of ground surface movements available from the technical literature for the area of interest, thus corroborating the choice of the most critical geomechanical parameters and relevant deformation properties of the rocks affecting subsidence.

Pharmacokinetics of diclofenac after oral administration of its potassium salt in sachet and tablet formulations

This paper reports the results of a pharmacokinetic study involving 24 healthy volunteers and designed to characterise the rate and extent of diclofenac absorption after the administration of a single dose of diclofenac (CAS 15307-86-5) potassium salt 50 mg in sachet (Voltfast) and tablet (Cataflam) formulations. Timed plasma concentrations of diclofenac during a 12-h-period after dosing were measured by means of HPLC with UV detection at 275 nm and a quantification limit of 10 ng/ml; the method was fully validated for pharmacokinetic purposes. These plasma concentrations were used to calculate Cmax, tmax, trapezoidal AUC0-t and AUC0-infinity and t1/2 by means of noncompartmental analysis. Cmax and tmax are the parameters expressing the rate of absorption, whereas the AUCs reflect the extent of absorption. The rate of absorption with the sachets proved to be very fast, reaching peak values at 10 min in seven subjects and at 15 min in the remaining subjects: mean time was 13.68 min, with concentrations at 5 min being 38% of Cmax. The average time to peak concentration with the tablets was 53.10 min. The extent of absorption of the sachets and tablets was similar, with AUC0-infinity values of respectively 1362 and 1214 ng.ml-1.h, and a 90% confidence interval 1.05-1.20. The highly soluble potassium salt of diclofenac was rapidly absorbed, especially in its sachet formulation, and thus appears to be an invaluable analgesic agent that is particularly useful for quick pain relief.

Gas chromatographic assay for estazolam in human plasma and results of a bioequivalence study

This paper describes a new sensitive gas chromatographic method with electron capture detector to assay estazolam in human plasma, which has been developed and validated for pharmacokinetic purposes. The drug and the internal standard (triazolam) were extracted from plasma buffered at pH 9.0 into toluene and analysed on a widebore DB 17 column. The calibration curve covered the 1.0-200 ng ml-1 range with a mean determination coefficient of 0.9996. The quantification limit was 1.0 ng ml-1. This method was used to investigate the bioequivalence of a new formulation of estazolam in drops (test) and the formulation in tablets (reference, ESILGAN). Both formulations were administered at a single dose of 2 mg in a clinical trial carried out on 24 healthy volunteers consisting of 12 males and 12 females, following a crossover randomised design in two periods with wash-out. The test and the reference formulations proved to be fully bioequivalent according to operating guidelines, namely through 90% confidence intervals in the 0.80-1.25 range.

Determination of ticlopidine in human plasma by high-performance liquid chromatography and ultraviolet absorbance detection

A simple HPLC method has been developed for the determination of ticlopidine in human plasma. Plasma samples were buffered at pH 9 and extracted with n-heptane-isoamyl alcohol (98.5:1.5, v/v). Imipramine was used as internal standard. Chromatography was performed isocratically with acetonitrile-methanol-0.05 M KH2PO4 (20:25:55, v/v) at pH 3.0 containing 3% triethylamine at a flow-rate of 1 ml/min. A reversed-phase column, Supelcosil LC-8-DB, 15 cm x 4.6 mm I.D., 5 microns particle size, was used. The effluent was monitored by UV absorbance detection at 235 nm. The method showed good accuracy, precision and linearity in the concentration range 5-1200 ng/ml. The limit of quantitation was 5 ng/ml, with a precision (C.V.) of 8.91%, which is the same as that achieved by other authors with a previously published GC-MS method. The procedure described in this paper is simple and allows the routine assessment of ticlopidine plasma concentration in pharmacokinetic studies following therapeutic doses in human subjects.

Determination of 2'-deoxy-5-iodouridine and its metabolite 5-iodouracil by high-performance liquid chromatography with ultraviolet absorbance detection in human serum

A new assay is described for 2'-deoxy-5-iodouridine, a drug employed as an antiviral agent by topical application. The parent drug, its systemic metabolite 5-iodouracil and an internal standard (5-iodouridine) were extracted from salted serum by an ethyl acetate partition at pH 6.7, back-extracted in alkalinized water and injected into a reversed-phase column. Potassium phosphate buffer-acetonitrile (95:5, v/v) eluted the analytes at a flow-rate of 1.5 ml/min. Detection was at 290 nm. The method proved to be linear in the 100-2000 ng/ml range.