Enhancement of nitric oxide solubility using Fe(II)EDTA and its removal by green algae <Emphasis Type="Italic">Scenedesmus</Emphasis> sp.

A photoautotrophic cultivation of green algae Scenedesmus cells was used for the removal of nitric oxide (NO) from a model flue gas mixture. In an attempt to improve the solubility of NO in the culture broth, the addition of Fe(II)EDTA to the cultivation was investigated. The addition of Fe(II)EDTA greatly enhanced NO-dissolution in the culture broth and subsequently increased the algal-uptake of NO. NO was assimilated as a source of nitrogen for the growth of Scenedesmus cells since there was a steady increase in cell density with no other nitrogen source in the culture except the incoming NO. 40–45% of NO removal was maintained for more than 12 days with the addition of 5 mM Fe(II)EDTA in a 1-L air-lift type photobioreactor system fed with 300 ppm of NO gas at a rate of 0.3 wm. However, the NO-dissolution-enhancing capacity of Fe(II)EDTA did not reach its full potential due to its oxidation to Fe(III)EDTA, possibly induced by molecular oxygen that evolved from algal photosynthesis, and subsequent loss of chelating capabilities.     

Continuous Cr(VI) removal by Scenedesmus incrassatulus in an airlift photobioreactor

Cr(VI) removal by Scenedesmus incrassatulus was characterized in a continuous culture system using a split-cylinder internal-loop airlift photobioreactor fed continuously with a synthetic effluent containing 1.0 mg Cr(VI) l^?1 at dilution rate (D) of 0.3 d^?1. At steady state, there was a small increase (6%) on the dry biomass (DB) concentration of Cr(VI)-treated cultures compared with the control culture. 1.0 mg Cr(VI) l^?1 reduced the photosynthetic pigments content and altered the cellular morphology, the gain in dry weight was not affected. At steady state, Cr(VI) removal efficiency was 43.5 ± 1.0% and Cr(VI) uptake was 1.7 ± 0.1 mg Cr(VI) g^?1 DB. The system reached a specific metal removal rate of 458 μg Cr(VI) g^?1 DB d^?1, and a volumetric removal rate of 132 μg Cr(VI) l^?1 d^?1.     

Bioreactor leaching of uranium from a low grade Indian silicate ore

Bio-leaching studies were carried out in a 2 L bioreactor- BIOSTAT-B^® equipped with a PLC based controller at 20–40% (w/v) pulp density using enriched culture of A.ferrooxidans for Turamdih uranium ore (Jharkhand, India). With the enriched culture of A.ferrooxidans adapted on Fe(II) at pH 2.0, 35 °C and 20% (w/v) pulp density, a 98.3% uranium recovery was recorded in 14 days. The leaching of uranium in the bioreactor improved the dissolution rate by reducing the time from 40 days in shake flask as per our earlier studies to 14 days. While investigating the importance of biogenic Fe(III) in the bio-leaching process a maximum recovery of 84.7% U₃O₈ was observed at pH 2.0 and 20% (w/v) pulp density in 10 h as compared to the uranium leaching of 38.3% in the control experiments. On raising the pulp density to 30%, uranium bio-recovery increased to 87.6% in 10 h at pH 2.0 with <76 μm size material. This showed a distinct advantage because of better mixing of slurry in the bioreactor with auto-controlled conditions that improved the kinetics.     

Quercetin is a substrate for the transmembrane oxidoreductase Dcytb

Duodenal cytochrome b (Dcytb) is a transmembrane oxidoreductase protein found in apical membranes of duodenal enterocytes, as well as human erythrocytes, with the capacity to transport electrons donated by cytosolic ascorbate to extracellular electron receptors such as Fe(III), dehydroascorbate, or molecular O₂. We have investigated the capacity of the flavonoid quercetin to act as an electron donor for Dcytb in a manner similar to that of ascorbate by observing the reduction of extracellular Fe(III) to Fe(II) in either Madin–Darby canine kidney (MDCK) cells overexpressing Dcytb (Dcytb⁺) or Dcytb-null MDCK cells. In Dcytb⁺ cells there is a saturable increase in extracellular Fe(III) reduction in response to increasing intracellular quercetin concentrations (K_m = 6.53 ± 1.57 μM), in addition to a small linear response, whereas in Dcytb-null cells there is only a small linear increase in extracellular Fe(III) reduction. No extracellular Fe(III) reduction occurs in Dcytb-null cells when the cells are preloaded with ascorbate. Flavonoids such as quercetin at their physiological concentrations can therefore function as modulators of ferric reductases, enhancing the import of Fe(II) and also providing extracellular reducing potential.     

Reduction of Fe(II)EDTA-NO by a newly isolated <Emphasis Type="Italic">Pseudomonas</Emphasis> sp. strain DN-2 in NO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> scrubber solution

Biological reduction of nitric oxide (NO) chelated by ferrous ethylenediaminetetraacetate (Fe(II)EDTA) to N₂ is one of the core processes in a chemical absorption–biological reduction integrated technique for nitrogen oxide (NO _x ) removal from flue gases. A new isolate, identified as Pseudomonas sp. DN-2 by 16S rRNA sequence analysis, was able to reduce Fe(II)EDTA-NO. The specific reduction capacity as measured by NO was up to 4.17 mmol g DCW⁻¹ h⁻¹. Strain DN-2 can simultaneously use glucose and Fe(II)EDTA as electron donors for Fe(II)EDTA-NO reduction. Fe(III)EDTA, the oxidation of Fe(II)EDTA by oxygen, can also serve as electron acceptor by strain DN-2. The interdependency between various chemical species, e.g., Fe(II)EDTA-NO, Fe(II)EDTA, or Fe (III)EDTA, was investigated. Though each complex, e.g., Fe(II)EDTA-NO or Fe(III)EDTA, can be reduced by its own dedicated bacterial strain, strain DN-2 capable of reducing Fe(III)EDTA can enhance the regeneration of Fe(II)EDTA, hence can enlarge NO elimination capacity. Additionally, the inhibition of Fe(II)EDTA-NO on the Fe(III)EDTA reduction has been explored previously. Strain DN-2 is probably one of the major contributors for the continual removal of NO _x due to the high Fe(II)EDTA-NO reduction rate and the ability of Fe(III)EDTA reduction.     

A new approach for Fe(III)EDTA reduction in NOx scrubber solution using bio-electro reactor

A new process for the removal of NO_x by a combined Fe(II)EDTA absorption and microbial reduction has been demonstrated, in which part of the Fe(II)EDTA will be oxidized by oxygen in the flue gas to form Fe(III)EDTA. In former studies, strain FR-2 has been found to reduce Fe(III)EDTA efficiently. Otherwise, it has been reported that bio-electro reactor could efficiently provide a chance for simultaneous denitrification and metal ion removal. Therefore, a use of bio-electro reactor is suggested to promote the reduction of Fe(III)EDTA by strain FR-2 in this paper. The results showed that the concentration of Fe(III)EDTA decreased rapidly when electric current was applied, and that as the current density rose, the Fe(III)EDTA reduction rate increased while followed by a decrease afterward. The formation of the biofilm on the electrode was observed by ESEM (Environmental Scan Electro-Microscope). In addition, the Fe(III)EDTA reduction rate obviously decreased with the existence of NaNO₂.     

Evaluation of in vitro free radical scavenging potential of Streptomyces sp. AM-S1 culture filtrate

The present study was carried out to determine the free radical scavenging potential of culture filtrate of Streptomyces sp. AM-S1. Antioxidant activity of culture filtrate, lyophilized culture filtrate and ethyl acetate extract of Streptomyces sp. AM-S1 was determined by various in vitro assays such as ferric reducing power assay, phosphomolybdenum reduction, DPPH and ABTS radical scavenging activities. The results revealed that the culture filtrate of Streptomyces sp. AM-S1 effectively scavenged DPPH (IC₅₀ 90.2 μl/ml) and ABTS (IC₅₀ 13.2 μl/ml) radicals in a concentration dependent manner. In all the assays, ethyl acetate extract registered higher antioxidant activity when compared with the lyophilized culture filtrate (LCF). In addition, ethyl acetate extract (1123.4 μmole Fe(II)/mg extract) exhibited higher ferric reducing activity than the standard BHA (814.4 μmole Fe(II)/mg extract). Further works are needed on the isolation and identification of antioxidant molecules from the ethyl acetate extract of Streptomyces sp. AM-S1 culture filtrate.     

Characterization of microbial communities removing nitrogen oxides from flue gas: the BioDeNOx process

BioDeNOx is an integrated physicochemical and biological process for the removal of nitrogen oxides (NOx) from flue gases. In this process, the flue gas is purged through a scrubber containing a solution of Fe(II)EDTA2-, which binds the NOx to form an Fe(II)EDTA.NO2- complex. Subsequently, this complex is reduced in the bioreactor to dinitrogen by microbial denitrification. Fe(II)EDTA2-, which is oxidized to Fe(III)EDTA- by oxygen in the flue gas, is regenerated by microbial iron reduction. In this study, the microbial communities of both lab- and pilot-scale reactors were studied using culture-dependent and -independent approaches. A pure bacterial strain, KT-1, closely affiliated by 16S rRNA analysis to the gram-positive denitrifying bacterium Bacillus azotoformans, was obtained. DNA-DNA homology of the isolate with the type strain was 89%, indicating that strain KT-1 belongs to the species B. azotoformans. Strain KT-1 reduces Fe(II)EDTA.NO2- complex to N2 using ethanol, acetate, and Fe(II)EDTA2- as electron donors. It does not reduce Fe(III)EDTA-. Denaturing gradient gel electrophoresis analysis of PCR-amplified 16S rRNA gene fragments showed the presence of bacteria closely affiliated with members of the phylum Deferribacteres, an Fe(III)-reducing group of bacteria. Fluorescent in situ hybridization with oligonucleotide probes designed for strain KT-1 and members of the phylum Deferribacteres showed that the latter were more dominant in both reactors.     

Evaluation of Fe(III)EDTA and Fe(II)EDTA-NO reduction in a NO x scrubber solution by magnetic Fe3O4-chitosan microspheres immobilized microorganisms

A two-stage bioreduction system containing magnetic-microsphere-immobilized denitrifying bacteria and iron-reducing bacteria was developed for the regeneration of scrubbing solutions for NO _x removal. In this process, a higher bioreduction rate and a better tolerance of inhibition of bacteria were achieved with immobilized bacteria than with free bacteria. This work focused on evaluation of the effects of the main components in the scrubbing solution on Fe(III)EDTA (EDTA: ethylenediaminetetraacetate) and Fe(II)EDTA-NO reduction, with an emphasis on mass transfer and the kinetic model of Fe(III)EDTA and Fe(II)EDTA-NO reduction by immobilized bacteria. It was found that Fe(II)EDTA-NO had a strong inhibiting effect, but Fe(II)EDTA had no effect, on Fe(III)EDTA reduction. Fe(II)EDTA accelerated Fe(II)EDTA-NO reduction, whereas Fe(III)EDTA had no effect. This showed that the use of the two stages of regeneration was necessary. Moreover, the effect of internal diffusion on Fe(III)EDTA and Fe(II)EDTANO reduction could be neglected, and the rate-limiting step was the bioreduction process. The reduction of Fe(III)EDTA and Fe(II)EDTA-NO using immobilized bacteria was described by a first-order kinetic model. Bioreduction can therefore be enhanced by increasing the cell density in the magnetic chitosan microspheres.     

An integrated bioreactor-expanded bed adsorption system for the removal of acetate to enhance the production of alpha-interferon-2b by Escherichia coli

A stirred tank bioreactor (STB) integrated with an expanded bed adsorption (EBA) system containing anion-exchange resin (Diaion WA30) was developed for in situ removal of acetate to increase the production of α-interferon-2b (α-PrIFN-2b) by Escherichia coli (E. coli). Although the total acetate (9.79 g/L) secreted by E. coli in the integrated STB/EBA system was higher than that in a bioreactor with dispersed resin or a conventional batch bioreactor, cell growth (14.97 g/L) and α-PrIFN-2b production (867.4 μg/L) were significantly improved owing to the high efficiency of acetate removal from the culture. The production of α-PrIFN-2b in the integrated STB/EBA system was improved by 3-fold and 1.4-fold over that obtained in a conventional batch bioreactor and a bioreactor containing dispersed resins, respectively.     

Treatment of dye (Remazol Blue) and heavy metals using yeast cells with the purpose of managing polluted textile wastewaters

The bioaccumulation of chromium(VI), nickel(II), copper(II), and reactive dye by the yeast Rhodotorula mucilaginosa has been investigated in media containing molasses as a carbon and energy source. Optimal pH values for the yeast cells to remove the pollutants were pH 4 for copper(II) and dye, pH 6 for chromium(VI) and dye, and pH 5 for nickel(II) and dye in media containing 50 mg l^?1 heavy metal and 50 mg l^?1 Remazol Blue. The maximum dye bioaccumulation was observed within 4–6 days and uptake yields varied from 93% to 97%. The highest copper(II) removal yields measured were 30.6% for 45.4 mg l^?1 and 32.4% for 95.9 mg l^?1 initial copper(II) concentrations. The nickel(II) removal yield was 45.5% for 22.3 mg l^?1, 38.0% for 34.7 mg l^?1, and 30.3% for 62.2 mg l^?1. Higher chromium(VI) removal yields were obtained, such as 94.5% for 49.2 mg l^?1 and 87.7% for 129.2 mg l^?1 initial chromium(VI) concentration. The maximum dye and heavy metal bioaccumulation yield was investigated in media with a constant dye (approximately 50 mg l^?1) and increasing heavy metal concentration. In the medium with 48.9–98.8 mg l^?1 copper(II) and constant dye concentration, the maximum copper(II) bioaccumulation was 27.7% and 27.9% whereas the maximum dye bioaccumulation was 96.1% and 95.3%. The maximum chromium(VI) bioaccumulation in the medium with dye was 95.2% and 80.3% at 48.2 and 102.2 mg l^?1 chromium(VI) concentrations. In these media dye bioaccumulation was 76.1% and 35.1%, respectively. The highest nickel(II) removal was 6.1%, 20.3% and 16.0% in the medium with 23.8 mg l^?1 nickel(II) + 37.8 mg l^?1 dye, 38.1 mg l^?1 nickel(II) + 33.4 mg l^?1 dye and 59.0 mg l^?1 nickel(II) + 39.2 mg l^?1 dye, respectively. The maximum dye bioaccumulation yield in the media with nickel(II) was 94.1%, 78.0% and 58.7%, respectively.     

The effect of molecular packing on the occurrence of spin crossover phenomena in one-dimensional Fe(II)-bis-Schiff base complexes

Two new one-dimensional Fe(II)-bis-Schiff base complexes, [Fe(L1)(pyz)] · CH₂Cl₂ (1) and [Fe(L2)(pyz)] · 2CH₂Cl₂ (2) (H₂L1 = bis(O-vanillin)-O-phenylenediimine, H₂L2 = bis(O-vanillin)-2,3-naphthalenediimine, pyz = pyrazine) are reported with their crystal structures and magnetic property. Compound 1 shows a two-step SCO behavior while 2 shows HS at all the temperature range measured. Although the extension of aromatic moiety from benzene (L1) to naphthalene (L2) was introduced for the purpose of strengthening the cooperativity, it leads to the absence of SCO, due to the unanticipated π–π interaction, which leads to the longer Fe–N bond lengths and a weak ligand field around Fe(II) ion.     

Conversion of squid pen by using Serratia sp. TKU020 fermentation for the production of enzymes,antioxidants, and N-acetyl chitooligosaccharides

A chitinase (CHT), a chitosanase (CHS) and a protease (PRO) were purified from the culture supernatant of Serratia sp. TKU020 with squid pen as the sole carbon/nitrogen source. The molecular masses of CHT, CHS and PRO determined by SDS-PAGE were approximately 65 kDa, 55 kDa and 55 kDa, respectively. CHT and CHS were inhibited by Mn²⁺, EDTA and PRO was inhibited by Mg²⁺, EDTA. The antioxidant activity of TKU020 culture supernatant was 78% (DPPH scavenging ability). N-Acetylglucosamine (GlcNAc) and N-acetyl chitobiose (GlcNAc)₂ were also produced from the culture supernatant by using TKU020 strain fermentation. The maximum production of GlcNAc and (GlcNAc)₂ was 1.3 mg/mL and 2.7 mg/mL, respectively, after 4 days of fermentation. With this method, we have shown that squid pen wastes can be utilized and it is effective in the production of enzymes, antioxidants, and N-acetyl chitooligosaccharides, facilitating its potential use in industrial applications and functional foods.     

NO removal in continuous BioDeNOx reactors: Fe(II)EDTA2- regeneration, biomass growth, and EDTA degradation

BioDeNOx is a novel technique for NOx removal from industrial flue gases. In principle, BioDeNOx is based on NO absorption into an aqueous Fe(II)EDTA2- solution combined with biological regeneration of that scrubber liquor in a bioreactor. The technical and economical feasibility of the BioDeNOx concept is strongly determined by high rate biological regeneration of the aqueous Fe(II)EDTA2- scrubber liquor and by EDTA degradation. This investigation deals with the Fe(II)EDTA2- regeneration capacity and EDTA degradation in a lab-scale BioDeNOx reactor (10-20 mM Fe(II)EDTA2-, pH 7.2 +/- 0.2, 55 degrees C), treating an artificial flue gas (1.5 m3/h) containing 60-155 ppm NO and 3.5-3.9% O2. The results obtained show a contradiction between the optimal redox state of the aqueous FeEDTA solution for NO absorption and the biological regeneration. A low redox potential (below -150 mV vs. Ag/AgCl) is needed to obtain a maximal NO removal efficiency from the gas phase via Fe(II)EDTA2- absorption. Fe(III)EDTA- reduction was found to be too slow to keep all FeEDTA in the reduced state. Stimulation of Fe(III)EDTA- reduction via periodical sulfide additions (2 mM spikes twice a week for the conditions applied in this study) was found to be necessary to regenerate the Fe(II)EDTA2- scrubber liquor and to achieve stable operation at redox potentials below -150 mV (pH 7.2 +/- 0.2). However, redox potentials of below -200 mV should be avoided since sulfide accumulation is unwanted because it is toxic for NO reduction. Very low values for biomass growth rate and yield, respectively, 0.043/d and 0.009 mg protein per mg ethanol, were observed. This might be due to substrate limitations, that is the electron acceptors NO and presumably polysulfide, or to physiological stress conditions induced by the EDTA rich medium or by radicals formed in the scrubber upon the oxidation of Fe(II)EDTA2- by oxygen present in the flue gas. Radicals possibly also induce EDTA degradation, which occurs at a substantial rate: 2.1 (+/-0.1) mM/d under the conditions investigated.     

Arsenic accumulation by aquatic macrophyte coontail (Ceratophyllum demersum L.) exposed to arsenite,and the effect of iron on the uptake of arsenite and arsenate

In this study, the aquatic macrophyte Ceratophyllum demersum L. (coontail or hornwort) was tested for its efficiency of arsenic (As) uptake under laboratory conditions. Our results revealed that the solution pH had a significant effect on As accumulation by C. demersum (p < 0.001). The accumulation was highest at pH 5 and decreased as pH values increased. Plants that were exposed to various concentrations of arsenite (As(III)) for 24 and 48 h, exhibited tolerance and toxic responses, respectively. As accumulation by C. demersum depended on the concentrations of As(III) and the duration of exposure (p < 0.001). At 40 μM after 24 h, plants accumulated 227.5 μg As g⁻¹ dw and showed no visible symptoms of toxicity. However, after 48 h, As level reached 302.4 μg g⁻¹ dw and biomass production decreased significantly. Toxic effects were evident by plant necrosis and negative biomass production, leading to a decrease in the amount of accumulated As. Also, the addition of iron (Fe) into the nutrient solutions (0.18 mM) had contrasting effects on the uptake of 2 As species – the uptake of As(III) was enhanced by the presence of Fe, but the uptake of arsenate (As(V)) was considerably inhibited.     

Oxidation of hydrogen sulphide in sour gas by Chlorobium limicola

The aim of this work was to assess the potential for bacterial oxidation of hydrogen sulphide as a purification method of sour gas. Using a continuous culture of Chlorobium limicola, high efficiencies of oxidation of both soluble and gaseous sulphide were achieved, with efficiencies for the latter exceeding 95%. Sulphide added as aqueous sodium sulphide was converted to sulphur and sulphate with almost total removal of the initial 100 mg S l⁻¹ within 24 h. Gaseous sulphide was oxidized at an efficiency of 95% (approximately 3 mmol S h⁻¹ (unit biomass Abs)⁻¹) over 1 h runs at a gas flow rate of 60 ml min⁻¹. With a sulphur recovery system to prevent sulphur accumulation, an efficiency of 70% was maintained. Biological removal of sulphide represents a potentially important biotechnological process, with high potential for viable scale up.     

Inductive influence of 4′-terpyridyl substituents on redox and spin state properties of iron(II) and cobalt(II) bis-terpyridyl complexes

A series of iron and cobalt bis-terpyridine (terpy) complexes were prepared with the general formula [M(R-terpy)₂](PF₆)₂, where M represents Co(II) and Fe(II), and R is the following terpyridine substituents in order of increasing electron-withdrawing behavior [(C₄H₈)N, (C₄H₉)NH, HO, CH₃O, CH₃-phenyl, H, Cl, CH₃SO, CH₃SO₂]. The complexes were prepared to investigate the extent of redox and spin state control that is attainable by simply varying the electron donating/withdrawing influence using a single substituent site on the terpyridine ligand. Cyclic voltammetry was used to assess the substituents influence on the M(III/II) redox couple. A plot of the M(III/II) redox potential (E_1/2) versus the electron donating/withdrawing nature of the substituents (Hammett constants), shows a strong linear trend for both metals; however, the substituents were observed to have a stronger influence on the Fe(III/II) couple. Solution magnetic susceptibility measurements at room temperature were carried out using standard NMR methodology (modified Evans method) where all of the Fe(II) complexes exhibited a diamagnetic, low spin (S = 0) behavior. In the cobalt series where R = H for [Co(R-terpy)₂]²⁺, the complex is known to be near the spin cross-over where the room temperature effective magnetic moment (μ_eff) in solution is ≈3.1 Bohr magnetons; however, in this study the μ_eff is observed to vary between 2.7 and 4.1 Bohr magnetons depending on the R-substituent.     

Effect of partial replacement of concentrates with jackfruit (Artocarpus heterophyllus) leaves on growth performance of kids grazing on native pasture of Tripura,India

Fifteen Black Bengal kids of about 3 months of age and body weight ranging from 3.8 to 4.9 kg were randomly distributed into three groups of five. Kids grazed native pasture 8 h/d. The kids in group I received supplementary concentrate (maize 35%, mustard cake 32%, rice bran 30%, mineral mixture 2% and common salt 1%) at approximately 2% of BW. However, 25 and 50% of the concentrate was replaced with jackfruit leaves for groups II and III, respectively. Total dry matter intake (DMI) was significantly higher in groups II and III than for group I due to greater forage consumption. Digestibility of CP (P < 0.05) decreased and that of NDF increased (P < 0.01) with increasing level of jackfruit leaves in the diet. Digestibility of ADF (P < 0.01), hemi cellulose (P < 0.05) and cellulose (P < 0.01) was higher in groups II and III in comparison to group I. Ruminal pH and TVFA concentration were not significantly different among the groups; however, rumen ammonia-N concentration decreased (P < 0.01) with increased level of jackfruit leaves in the diet. Similarly, plasma urea nitrogen and blood glucose levels were also reduced (P < 0.05) with increasing level of jackfruit leaves in the diet Average daily gain (ADG) was 47.33, 45.11 and 35.56 g/d in groups I, II and III, respectively. ADG and DMI/kg gain were not adversely affected when the level of replacement was restricted to 25%; however, at the 50% of replacement both parameters were adversely affected (P < 0.05). From the results of this experiment, it was concluded that jackfruit leaves might replace 25% of the supplemental concentrate for growing kids grazing in native pasture of northeast India.     

Synthesis and hyperpolarisation of eNOS substrates for quantification of NO production by 1H NMR spectroscopy

Hyperpolarization enhances the intensity of the NMR signals of a molecule, whose in vivo metabolic fate can be monitored by MRI with higher sensitivity. SABRE is a hyperpolarization technique that could potentially be used to image nitric oxide (NO) production in vivo. This would be very important, because NO dysregulation is involved in several pathologies, including cardiovascular ones. The nitric oxide synthase (NOS) pathway leads to NO production via conversion of l-arginine into l-citrulline. NO is a free radical gas with a short half-life in vivo (≈5 s), therefore direct NO quantification is challenging. An indirect method – based on quantifying conversion of an l-Arg- to l-Cit-derivative by ¹H NMR spectroscopy – is herein proposed. A small library of pyridyl containing l-Arg derivatives was designed and synthesised. In vitro tests showed that compounds 4a–j and 11a–c were better or equivalent substrates for the eNOS enzyme (NO₂^? production = 19–46 μM) than native l-Arg (NO₂^? production = 25 μM). Enzymatic conversion of l-Arg to l-Cit derivatives could be monitored by ¹H NMR. The maximum hyperpolarization achieved by SABRE reached 870-fold NMR signal enhancement, which opens up exciting future perspectives of using these molecules as hyperpolarized MRI tracers in vivo.     

Comparative efficiency of algal biofilters in the removal of chromium and copper from wastewater

The performance of a macroalgae (Sargassum sp.), a laboratory-cultivated microalgae (Chlorococcum sp.) and a commercially available granulated activated carbon (GAC) for the removal of copper (Cu) and chromium (Cr) from aqueous solutions was evaluated using batch experiments. Kinetic and isotherm experiments were done at the optimal pH of 4.5 ± 0.1 for Cu (II) and 2.0 ± 0.1 for Cr (total). The equilibrium isotherms were determined and the results were analyzed using the Langmuir and Freundlich models. The best Cu removal performance was observed on Sargassum at a maximum removal of 87.3% obtained for an initial concentration of 20 mg L^?1 Cu. The maximum uptake capacities for Cu (II) were 71.4, 19.3 and 11.4 mg g^?1 of Sargassum, Chlorococcum and GAC, respectively. The biosorbents were also able to remove appreciable amounts of Cr, again with Sargassum showing maximum uptake capacity over the other materials. Kinetic studies also reveal that the removal rate is faster for both metals in Sargassum. Tests with an actual wastewater confirm the maximum uptake capacity of Cu by Sargassum. In all experiments the Sargassum biofilter outperformed GAC, which makes it a promising low-cost alternative to conventional filtration materials for wastewater treatment.