Biosynthesis Pathways, Transport Mechanisms and Biotechnological Applications of Fungal Siderophores

Iron (Fe) is the fourth most abundant element on earth and represents an essential nutrient for life. As a fundamental mineral element for cell growth and development, iron is available for uptake as ferric ions, which are usually oxidized into complex oxyhydroxide polymers, insoluble under aerobic conditions. In these conditions, the bioavailability of iron is dramatically reduced. As a result, microorganisms face problems of iron acquisition, especially under low concentrations of this element. However, some microbes have evolved mechanisms for obtaining ferric irons from the extracellular medium or environment by forming small molecules often regarded as siderophores. Siderophores are high affinity iron-binding molecules produced by a repertoire of proteins found in the cytoplasm of cyanobacteria, bacteria, fungi, and plants. Common groups of siderophores include hydroxamates, catecholates, carboxylates, and hydroximates. The hydroxamate siderophores are commonly synthesized by fungi. L-ornithine is a biosynthetic precursor of siderophores, which is synthesized from multimodular large enzyme complexes through non-ribosomal peptide synthetases (NRPSs), while siderophore-Fe chelators cell wall mannoproteins (FIT1, FIT2, and FIT3) help the retention of siderophores. S. cerevisiae, for example, can express these proteins in two genetically separate systems (reductive and nonreductive) in the plasma membrane. These proteins can convert Fe (III) into Fe (II) by a ferrous-specific metalloreductase enzyme complex and flavin reductases (FREs). However, regulation of the siderophore through Fur Box protein on the DNA promoter region and its activation or repression depend primarily on the Fe availability in the external medium. Siderophores are essential due to their wide range of applications in biotechnology, medicine, bioremediation of heavy metal polluted environments, biocontrol of plant pathogens, and plant growth enhancement.

Prospecting for underground natural hydrogen - new energy for the future

Hydrogen, accounting for 75% of ordinary matter by mass and over 90% by atomic number, is the third most abundant element on the Earth's surface, mainly in the form of chemical compounds such as water and hydrocarbons. When burned, hydrogen gas (H2) produces heat and water without causing environmental pollution, thus it is expected to be one of the clean energy sources for the future. Industrial hydrogen has so far been mainly produced by thermochemical processes of fossil fuels such as coal and natural gas, and insignificantly by electrolysis of water. Recent natural hydrogen discoveries recorded in the world, especially the exploration and discovery of relatively pure underground hydrogen which was extracted and used as fuel for a local power generator in Bourakebougou (Mali), show the possibility of prospecting for underground natural hydrogen. The article provides an overview of natural hydrogen discoveries over the world and gives recommendations on the prospecting for underground natural hydrogen in Vietnam.

Copper Oxide-Based Photocatalysts and Photocathodes: Fundamentals and Recent Advances

This work aims at reviewing the most impactful results obtained on the development of Cu-based photocathodes. The need of a sustainable exploitation of renewable energy sources and the parallel request of reducing pollutant emissions in airborne streams and in waters call for new technologies based on the use of efficient, abundant, low-toxicity and low-cost materials. Photoelectrochemical devices that adopts abundant element-based photoelectrodes might respond to these requests being an enabling technology for the direct use of sunlight to the production of energy fuels form water electrolysis (H2) and CO2 reduction (to alcohols, light hydrocarbons), as well as for the degradation of pollutants. This review analyses the physical chemical properties of Cu2O (and CuO) and the possible strategies to tune them (doping, lattice strain). Combining Cu with other elements in multinary oxides or in composite photoelectrodes is also discussed in detail. Finally, a short overview on the possible applications of these materials is presented.

Síntese, caracterização e estabilidade de nanopartículas de magnetita

Nanopartículas de ferro são muito utilizadas em diversas áreas de pesquisa. O elemento químico ferro (Fe), sendo o quarto elemento mais abundante na crosta terrestre, e a substância mineral magnetita, com propriedade magnética, apresentam aplicações nas áreas industrial, ambiental, biomédica e de novas tecnologias. Este trabalho apresenta processo de síntese de nanopartículas partindo-se de sais precursores, bem como a caracterização dos produtos e as rotas para estabilizá-los. Os sais químicos precursores utilizados foram o cloreto férrico (FeCl3) e o sulfato ferroso (FeSO4) na proporção de 2:1, sob agitação por ultrassom e pH ácido. Para formação do precipitado de nanopartículas usou-se solução aquosa de hidróxido de sódio (NaOH) de pH 12. A difratometria de raio-X, mostra a presença de magnetita (Fe3O4) indicada pelos picos característicos de difração em graus 2Ө = 18° (largo), 31° (fino), 36° (bem definido), 43,4°, 45°, 53,6°, 57,7°, 63,3°. A microscopia eletrônica de transmissão mostra a morfologia dos produtos da síntese. Fatores que influenciam a estabilidade das partículas são agitação, o ajuste de pH, condições de secagem. O tamanho médio das nanopartículas de magnetitas é de aproximadamente 15 nm. Iron nanoparticles are widely used in several research areas. The chemical element iron (Fe), being the fourth most abundant element in the earth's crust, and the mineral substance magnetite, with magnetic properties, have applications in industrial, environmental, biomedical, and new technology areas. This work presents the process of synthesis of nanoparticles starting from precursor salts, as well as the characterization of the products and the routes to stabilize them. The precursor chemical salts were ferric chloride (FeCl3) and ferrous sulfate (FeSO4) in a 2:1 ratio, under ultrasound agitation and acidic pH. For the nanoparticles growth was applied aqueous solution of sodium hydroxide (NaOH) at pH 12. X-ray diffraction shows the presence of magnetite (Fe3O4) indicated by characteristic diffraction peaks in degrees 2Ө = 18° (wide), 31° (fine), 36° (well defined), 43.4°, 45°, 53.6°, 57.7°, 63.3°. Scanning electron microscopy shows the morphology of the synthesis products. Factors that influence the stability of the particles are agitation, the pH adjustment, and the conditions of drying. The average size of the magnetite nanoparticles is approximately 15 nm.

Identification of Explosion from Hydrogen Gas

Hydrogen or sometimes called water, is a chemical element on the periodic table that has the symbol H and atomic number 1. At standard temperatures and pressures, hydrogen is colorless, odorless, non-metallic, singlevalent, and a highly flammable diatomic gas. With an atomic mass of 1.00794 amu, hydrogen is the lightest element in the world. It is also the most abundant element, accounting for roughly 75% of the total elemental mass of the universe. Most stars are formed by hydrogen in the plasma state. Hydrogen compounds are relatively rare and rarely found naturally on Earth, and are usually produced industrially from various hydrocarbons such as methane. Hydrogen can also be produced from water through electrolysis, but this process is more expensive commercially than producing hydrogen from natural gas. With the aim to prove the explosion that occurred and the reaction that occurred during the experimental process of an exothermic or endoderm reaction explosion

Proximate, mineral and melissopalynological analyses of honeys produced by Apis mellifera adansonii maintained at the University of Lagos Apiary

This study focused on the management of established Apis mellifera adansonii colonies, and evaluation of the proximate, mineral, and pollen contents of honeys produced by these bees at the University of Lagos apiary. Two newly established bee colonies were managed using modern hive management techniques. Honeys produced by these colonies were subjected to further laboratory analyses. Proximate composition of honey samples was determined based on the official analysis methods from Association of Official Analytical Chemists (AOAC). Mineral composition was determined quantitatively using atomic absorption spectroscopy (AAS). Melissopalynological analysis was conducted to ascertain the amount, type and origin of pollen present in the samples. On the basis of the proximate composition, colony 1 honey had higher carbohydrate (81.29%), crude fibre (1.43%) and ash contents (0.70%) while colony 2 honey recorded higher protein (2.72%), crude fat (0.17%), moisture content (17.32%) and pH (4.6). Result of the mineral analysis showed that potassium was the most abundant element, while manganese was the least present trace element in both honeys. Investigated honey samples contained 8609 pollen and spore types belonging to 27 families and 29 species. Colony 1 honey had the highest pollen diversity, while colony 2 honey recorded the highest abundance. Hippocratea sp. was the predominant pollen type in colony 1 honey sample while Phyllantus sp. was the secondary dominant species in colony 2 honey. Celastraceae and Rubiaceae were the most dominant families recorded in the investigated honey samples. Investigated honey samples were multifloral, rich in minerals, and met the standard requirements of good honey as recommended by International Honey Commission. The study provided the basis for identification of major plants visited by Apis mellifera honeybees within the apiary. There is a need to conserve the existing flora within the study location, especially those found to be rewarding to Apis mellifera adansonii.

Dispersion of Natural Airborne TiO2 Fibres in Excavation Activity as a Potential Environmental and Human Health Risk

Titanium is the ninth most abundant element, approximately 0.7% of the Earth crust. It is used worldwide in large quantities for various applications. The IARC includes TiO2 in Group 2B as possibly carcinogenic to humans suggesting that pathological effects correlate to particle size and shape. This study case quantifies the release of natural TiO2 particles during mining activity, involving meta-basalt and shale lithologies in the Ligurian Alps, during excavation of the Terzo Valico as part of the Trans-European Transport Network. Type, width, length, aspect ratio, and concentration of TiO2 particles in needle habit were determined. The different samplings have reported that airborne concentrations in meta-basalt were 4.21 ff/L and 23.94 ff/L in shale. In both cases, the concentration never exceeds the limits established by various organizations for workers health protection. Nevertheless, TiO2 elongated particles, recognized as rutile, showed the dimensional characteristic of fibres, as reported by WHO. These fibres deserve particular attention because they can reach the alveolar space and trigger inflammation and chronic diseases. The results indicate that monitoring the TiO2 in both working environments and Ti-rich geological formations, associated with epidemiological studies, may represent a useful tool to determine the exposure risk of workers and the general population.

Vitamin D Supplements: Over-the-Counter Accessibility... It Is Safe?

Calcium is the fifth most abundant element in earth and human body. It has multiple functions within our system such bone mineralization, neuromuscular excitability regulation, hemostasis, membrane transport, release of hormones and neurotransmitters, among others. For duodenal absorption of calcium, we need vitamin D, reason for which supplementation of both components is important to maintain adequate calcium homeostasis. However, it is entirely beneficial or can be harmful? As we know everything in excess has its consequences, as we describe below. 72 y/o male is brought to the ED after relative find him lethargic, she reports noticing generalized weakness that has been progressing over weeks, prominent in upper extremities with associated increased in urinary frequency. Patient past medical history is relevant for CAD, hypothyroidism, dyslipidemia, and DMT2. On physical examination patient is found hypoactive, but arousable to verbal stimuli, without distress, focal neurologic deficit, thyromegaly nor lymphadenopathy. Presents with Ca+: 18.8mg/dL (n:8.0–10.5mg/dL), that could explain patient clinical presentation for which workup for hypercalcemia is done finding PTH suppress: 14.57pg/mL (n:15-65pg/mL). Patient now with non-PTH related hypercalcemia is further evaluated and found with negative UPEP and SPEP ruling out multiple myeloma and PTH-rp <2.0pmol/L (negative). While etiology of severe hypercalcemia is being study, patient complications of it are being managed such as AKI stage 3 as he presents with Cr: 3.85mg/dL, BUN: 62.5, CrCl:18ml/min and GFR: 15ml/min. Aggressive IV hydration and bisphosphonate therapy failed to decrease calcium and renal function continues worsens, for which hemodialysis is required for calcium clearance. Patient then found with vitamin D25-OH levels: 210.4ng/mL (n:30-100ng/mL), upon questioning he reports taking multivitamins and supplements equivalent for a daily ingestion of 50,700IU of Vitamin D3 and 334mg of calcium carbonate. Patient calcium levels normalize after dialysis but develops renal failure for which he has to be discharged on permanent hemodialysis. Although prevalence is unknown, hypercalcemia due to vitamin D intoxication is relatively uncommon in comparison to hyperparathyroidism and malignancy. An exact dose intake that leads to intoxication has not yet being stablished but supplementation besides dosage is also dependent on duration of therapy. This case has a lot to teach us, starting with detrimental effects of hypercalcemia, follow by the consequences of lack of counseling and close follow-up of patient over-the-counter supplementation. As physicians we should inquire more about OTC medications and supplements our patients are taking not only for intoxication concerns, but also for drugs interactions. Counseling must be the cornerstone of our practice to avoid life changing consequences as in this case.

Real-time imaging of Na+ reversible intercalation in “Janus” graphene stacks for battery applications

Sodium, in contrast to other metals, cannot intercalate in graphite, hindering the use of this cheap, abundant element in rechargeable batteries. Here, we report a nanometric graphite-like anode for Na+ storage, formed by stacked graphene sheets functionalized only on one side, termed Janus graphene. The asymmetric functionalization allows reversible intercalation of Na+, as monitored by operando Raman spectroelectrochemistry and visualized by imaging ellipsometry. Our Janus graphene has uniform pore size, controllable functionalization density, and few edges; it can store Na+ differently from graphite and stacked graphene. Density functional theory calculations demonstrate that Na+ preferably rests close to -NH2 group forming synergic ionic bonds to graphene, making the interaction process energetically favorable. The estimated sodium storage up to C6.9Na is comparable to graphite for standard lithium ion batteries. Given such encouraging Na+ reversible intercalation behavior, our approach provides a way to design carbon-based materials for sodium ion batteries.

Analysis of Selected Minerals in Homemade Grape Vinegars Obtained by Spontaneous Fermentation

Fruit vinegars are widely used as a spice and food preservative. They are considered as functional food, containing many bioactive compounds with pro-health benefits. Grape vinegars can be also a source of mineral compounds. Their quantity and diversity can be determined by environmental factors and growing conditions, such as temperature, mineral composition of the soil, heavy metal contamination, sunlight availability as well as grape variety and fruit ripeness stage. The aim of the study was to determine the content of minerals in homemade grape vinegars, obtained by spontaneous fermentation. Five different grape (Vitis vinifera L.) varieties were used in the study (Cabernet Cortis, Johanniter, Solaris, Souvignier gris and Prior). Moreover, the effect of sugar addition in the fermentation process on the mineral content was examined. The mineral content was determined using the ICP-OES method. Among the analysed samples, potassium was the most abundant element (936.07–1472.3 mg/L of vinegar). Comparative analysis showed that the content of Ca, Fe and Cr was significantly higher in vinegars prepared from red varieties than in white-coloured ones. In turn, vinegars prepared from white grape varieties contained statistically significantly higher content of potassium. Vinegar colour did not have a significant influence on the content of the remaining elements included in the analysis. Furthermore, statistical analysis did not reveal any significant differences in the content of the analysed minerals in any of the grape varieties used between the samples with and without sugar addition.