| 1. |
- Ginesy, Mireille, et al.
(författare)
-
Simultaneous Quantification of L-Arginine and Monosaccharides during Fermentation : An Advanced Chromatography Approach
- 2019
-
Ingår i: Molecules. - : MDPI. - 1431-5157 .- 1420-3049. ; 24:4
-
Tidskriftsartikel (refereegranskat)abstract
- Increasing demand for L-arginine by the food and pharmaceutical industries has sparked the search for sustainable ways of producing it. Microbial fermentation offers a suitable alternative; however, monitoring of arginine production and carbon source uptake during fermentation, requires simple and reliable quantitative methods compatible with the fermentation medium. Two methods for the simultaneous quantification of arginine and glucose or xylose are described here: high-performance anion-exchange chromatography coupled to integrated pulsed amperometric detection (HPAEC-IPAD) and reversed-phase ultra-high-performance liquid chromatography combined with charged aerosol detection (RP-UHPLC-CAD). Both were thoroughly validated in a lysogeny broth, a minimal medium, and a complex medium containing corn steep liquor. HPAEC-IPAD displayed an excellent specificity, accuracy, and precision for arginine, glucose, and xylose in minimal medium and lysogeny broth, whereas specificity and accuracy for arginine were somewhat lower in medium containing corn steep liquor. RP-UHPLC-CAD exhibited high accuracy and precision, and enabled successful monitoring of arginine and glucose or xylose in all media. The present study describes the first successful application of the above chromatographic methods for the determination and monitoring of L-arginine amounts during its fermentative production by a genetically modified Escherichia coli strain cultivated in various growth media.
|
|
| 2. |
- Ginesy, Mireille, et al.
(författare)
-
Tuning of the Carbon-to-Nitrogen Ratio for the Production of L-Arginine by Escherichia coli
- 2017
-
Ingår i: Fermentation. - : MDPI. - 2311-5637. ; 3:4
-
Tidskriftsartikel (refereegranskat)abstract
- L-arginine, an amino acid with a growing range of applications within the pharmaceutical, cosmetic, food, and agricultural industries, can be produced by microbial fermentation. Although it is the most nitrogen-rich amino acid, reports on the nitrogen supply for its fermentation are scarce. In this study, the nitrogen supply for the production of l-arginine by a genetically modified Escherichia coli strain was optimised in bioreactors. Different nitrogen sources were screened and ammonia solution, ammonium sulphate, ammonium phosphate dibasic, and ammonium chloride were the most favourable nitrogen sources for l-arginine synthesis. The key role of the C/N ratio for l-arginine production was demonstrated for the first time. The optimal C/N molar ratio to maximise l-arginine production while minimising nitrogen waste was found to be 6, yielding approximately 2.25 g/L of l-arginine from 15 g/L glucose with a productivity of around 0.11 g/L/h. Glucose and ammonium ion were simultaneously utilized, showing that this ratio provided a well-balanced equilibrium between carbon and nitrogen metabolisms.
|
|
| 3. |
- Maslova, Marina, et al.
(författare)
-
Aluminum adsorption on titanium phosphate and silica-modified titanium phosphates
- 2009
-
Ingår i: The Natural History of Aluminium : From Non-Selection to Natural Selection. ; , s. 41-
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Synthesis, characterization and sorption affinities of titanium phosphate (TiP) and titanium phosphate silicates (TiPSi) in relation to various metal ions were recently reported by our group. In this work, we explored further adsorption properties of these materials with respect to aluminium ions in aqueous solutions. Sorption of Al3+(aq) increases with pH and reaches ca. 13 mg/g at pH close to neutral conditions and it can be described by an ion-exchange mechanism. Surface speciation of aluminium was studied by 27Al and 31P solid state NMR. These and other spectroscopic data were correlated with adsorption macroscopic measurements. Purification of process and drinking waters is one of the potential applications of these cheap adsorbents manufactured by decomposition of mineral sphene, CaTiOSiO4, which is abundant up to 5 % in tailings of apatite ores in Kola peninsula.
|
|
| 4. |
- Maslova, Marina, et al.
(författare)
-
Formation of titanium phosphate composites during phosphoric acid decomposition of natural sphene
- 2008
-
Ingår i: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596 .- 1095-726X. ; 181:12, s. 3357-3365
-
Tidskriftsartikel (refereegranskat)abstract
- Decomposition of mineral sphene, CaTiOSiO4, by H3PO4 is investigated in detail. During the dissolution process, simultaneous calcium leaching and formation of titanium phosphate (TiP) take place. The main product of decomposition is a solid titanium phosphate-silica composite. The XRD, solid-sate NMR, IR, TGA, SEM and BET data were used to identify and characterize the composite as a mixture of crystalline Ti(HPO4)2H2O and silica. When 80% phosphoric acid is used the decomposition degree is higher than 98% and calcium is completely transferred into the liquid phase. Formation of Ti(HPO4)2H2O proceeds via formation of meta-stable titanium phosphate phases, Ti(H2PO4)(PO4)2H2O and Ti(H2PO4)(PO4).The sorption affinities of TiP composites were examined in relation to caesium and strontium ions. A decrease of H3PO4 concentration leads to formation of composites with greater sorption properties. The maximum sorption capacity of TiP is observed when 60% H3PO4 is used in sphene decomposition.The work demonstrates a valuable option within the Ti(HPO4)2H2O-SiO2 composite synthesis scheme, to use phosphoric acid flows for isolation of CaHPO42H2O fertilizer.
|
|
| 5. |
- Maslova, Marina, et al.
(författare)
-
Synthesis, characterization, and sorption properties of amorphous titanium phosphate and silica-modified titanium phosphates
- 2008
-
Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 47:23, s. 11351-11360
-
Tidskriftsartikel (refereegranskat)abstract
- Amorphous titanium hydroxyphosphate with formula Ti(OH)1.36(HPO4)1.322.3H2O and a new silica-modified titanium hydroxyphosphate with a general formula Ti(OH)2x(HPO4)2-xySiO2nH2O are synthesized and characterized using IR, TG, XRD, SEM, solid-state NMR, and BET techniques. It is concluded that SiO2 is evenly distributed within the titanium phosphate (TiP) agglomerates and that neither the separate silica phase nor the titanium silicates are formed during the synthesis of silica-modified titanium hydroxyphosphate. Correlations between the texture, ion-exchange properties of the amorphous titanium hydroxyphosphate, and the amount of SiO2 present within the TiP matrix are established. Sorption properties of silica-modified titanium hydroxyphosphate toward Cs+ and Sr2+ are studied in a series of samples with an increasing amount of silica, at different pH, and in NaCl solutions with a varying ionic strength. It is found that sorption of Cs+ does not depend practically on the amount of SiO2 present, whereas the Sr2+ uptake drastically decreases with an increase of silica amount. The effects of pH and of the electrolyte concentration on the sorption behavior of titanium phosphate are discussed in terms of ionic hydration shell and titanium phosphate structural specificity. The kinetics of sorption processes is also investigated, and the diffusion coefficients for cesium and strontium are obtained.
|
|
| 6. |
- Maslova, Marina V., et al.
(författare)
-
Extended study on the synthesis of amorphous titanium phosphates with tailored sorption properties
- 2012
-
Ingår i: Journal of Non-Crystalline Solids. - : Elsevier BV. - 0022-3093 .- 1873-4812. ; 358:22, s. 2943-2950
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of concentrations of both TiO2 and H2SO4 in the syntheses of amorphous titanium phosphates (TiP) is reported. IR, XRD, TGA, BET and NMR techniques were used to characterise the isolated TiP products. The concentration of sulphuric acid in the initial synthesis plays a major role in the structural diversity and sorption properties of the final ionites. In the primary solutions, Ti(IV) is in monomeric, polymeric and colloidal forms. Upon addition of H3PO4 the presence of monomeric titanium ensures formation of the Ti(HPO4)2 phase. The polymeric Ti(IV) is responsible for formation of the titanium hydroxo-phosphate phase, Ti(OH)2(HPO4), whilst the colloidal form of Ti(IV) appears to have a role in coagulation of a minor Ti(OH)4 phase in an amorphous TiP. It is found that TiP ion-exchange capacities gradually increase with an increase of both TiO2 and H2SO4 concentrations and reach a maximum value of 3.8 mg-eq g− 1 when TiO2 is 70–100 g L− 1 and H2SO4 is 480–560 g L− 1. Analyses of compositional, structural and sorption data allowed 3D correlation diagrams to be built that can facilitate fabrication of TiP with tailored sorption properties.
|
|
| 7. |
- Rusanova, Daniela
(författare)
-
31 P- and 65 Cu- solid state NMR studies of Cu(I) di-alkyl-dithiophosphates : complex Formation Mechanism on Synthetic Chalcocite Surfaces
- 2004
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Alkyl substituted derivatives of dithiophosphoric acid are frequently used as collectors in froth flotation enrichment of copper sulfide ores. Due to interaction between Cu atoms at the surface and thiol collector molecules, a concomitant adsorption process occurs on the mineral surface. The presence of Cu(I) di-alkyl-dithiophosphate species on the Cu2S surfaces has been reported. However, to date, a more detailed description of the identification and composition of these species, has not been given and the processes leading to their formation are still not fully understood. In this work, polycrystalline Cu(I) di-alkyl-dithiophosphate complexes were synthesized and studied by 31P CP/MAS and static 65Cu NMR spectroscopy. Further investigation on crystal habits of these systems was carried out by powder X-ray Diffraction and Scanning Electron Microscopy. Copper(I) di-alkyl-dithiophosphate complexes exist only in the solid state and form tetra-, hexa- or octanuclear clusters with four or six bridging dithiophosphate ligands, respectively. A combined approach of the aforementioned techniques allowed the determination the type of Cu(I) dithiophosphate clusters. A cluster rearrangement process occurring during the recrystallization of these clusters in halogen-containing solvents is described. An equilibrium between different Cu(I) dithiophosphate (dtp) complexes and a solvent effect are discussed in terms of a specific donor- acceptor (D-A) interaction. Three different di-alkyl-dithiophosphates, potassium salts (KEt2dtp, KiPr2dtp and KiBu2dtp), were used for the investigation of the changes on synthetic chalcocite surfaces after collector treatment. The morphology of conditioned Cu2S surfaces was observed with SEM. A comparative analysis of the 31P chemical shift data estimated from the experimental NMR spectra of the polycrystalline Cu(I) dithiophosphate complexes was used for assigning the 31P resonance lines from the collector treated mineral surfaces. 31P chemical shift data (both isotropic chemical shifts and chemical shift anisotropy (CSA) data) of the species formed on the synthetic Cu2S surfaces allowed to assign these species to polycrystalline phases of: (i) Cu6L6 with L = Et2dtp¯, (ii) Cu4L4 with L = iPr2dtp¯ and (iii) Cu8L6(S) and Cu6L6 with L = iBu2dtp¯, respectively. A heterophase autocatalytic step process of the formation and growth of solid CuxLy (L= di-alkyl-dithiophosphate; x = 4, 6 or 8 and y=4 or 6) complexes on the surface of Cu2S is proposed. A possible role of the oxidized form of the dithiophosphate collector, bis[di(alkyl)thiophosphoryl] disulfane (disulfide), is discussed in terms of a specific self-redox interaction.
|
|
| 8. |
- Rusanova, Daniela
(författare)
-
An NMR synopsis of the coordination chemistry of copper(I) dithiophosphate clusters
- 2006
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The coordination chemistry of monovalent copper with O,O'- dialkyldithiophosphate chelating ligands (L = S2P(OR)2, R = alkyl) is presented by poly-nuclear clusters containing Cu4 (tetrahedral), Cu6 (trigonal antiprismatic) or Cu8 (cubic) cores where the ligands display a tri-metallic tri-connective coordination mode in the first two classes of structures (Cu4L4 and Cu6L6) and a tetra-metallic tetra-connective coordination pattern in the third class (Cu8L6(S)). In this work, the polycrystalline copper(I) O,O'-dialkyldithiophosphate (dtp) compounds - Cu4L4 (L = S2P(OiPr)2, Cu6L6 (L = S2P(OEt)2) and Cu8L6(S) (L = S2P(OR)2, R = Et, nPr, iPr, nBu, iBu and iAm) were synthesised and studied by 31P MAS and static 65Cu NMR spectroscopy. The Copper K-edge EXAFS spectroscopy was used to obtain information about the copper cores in the aforementioned cluster compounds and the structural units in the polycrystalline samples were confirmed by the FAB-mass data. Further investigation on the crystal habits of these systems was carried out by powder X-ray Diffraction and Scanning Electron Microscopy (SEM). Additional 65Cu NMR experiments were performed to determine the transverse relaxation time constants, T2, for Cu8L6(S) (L = S2P (OR)2, R = iPr, nBu and iAm). Possible intra- and inter-molecular motions in the octa-nuclear cluster structures in terms of size and branching of the hydrocarbon chains are discussed as reasons for the different 65Cu NMR responses of the systems. Alkyl substituted derivatives of dithiophosphoric acid are frequently used as collectors in the froth flotation of copper sulphide ores. Due to interactions between copper atoms at the surface and thiol molecules, a concomitant adsorption process occurs on the mineral surface. The presence of copper(I) O,O¢-dialkyldithiophosphate species on the chalcocite (Cu2S) surfaces has been revealed, however to date, a detailed description of the composition and/or chemical identification of these species has not been reported, and the processes leading to their formation are not yet understood. Four different O,O'-dialkyldithiophosphate, potassium salts (KEt2dtp, KiPr2dtp, KiBu2dtp and KiAm2dtp and a disulphide - (iAm2dtp)2 ), were used to investigate the changes on synthetic chalcocite surfaces treated with a collector/disulphide, and morphologies of conditioned surfaces were monitored with SEM. Comparative analyses of the 31P isotropic chemical shift and chemical shift anisotropy (CSA) data of the polycrystalline copper(I) O,O'-dialkyldithiophosphate cluster were used for assigning the 31P resonance lines of the species at the collector treated mineral surfaces. The data allowed the species to be assigned to polycrystalline phases of: (i) Cu6L6 with L = Et2dtp¯, (ii) Cu4L4 with L = iPr2dtp¯, iii) Cu8L6(S) and Cu6L6 with L = iBu2dtp¯, and iiii) Cu8L6(S) with L = iAm2dtp¯, respectively. These are formed in a reaction where copper(I) from the chalcocite surface is oxidised to copper(II), before being reduced back by the dtp - molecules to copper(I) in copper(I) O,O'- dialkyldithiophosphate cluster compounds. A heterophase autocatalytic outgrowth of these copper(I) O,O'-dialkyldithiophosphate species on the chalcocite surface is proposed and the role of the oxidised form of the dithiophosphate collector, disulphide, is discussed in terms of a specific self-redox interaction.
|
|
| 9. |
- Rusanova, Daniela, et al.
(författare)
-
Copper(I) O,O '-dialkyldithiophosphate clusters : EXAFS, NMR and X-ray diffraction studies
- 2007
-
Ingår i: Journal of coordination chemistry (Print). - : Informa UK Limited. - 0095-8972 .- 1029-0389. ; 60:5, s. 517-525
-
Tidskriftsartikel (refereegranskat)abstract
- Copper K- edge EXAFS data for six polycrystalline cubic cluster compounds, {Cu-8[ S2P(OR)(2)](6)(mu(8)- S)} with R= Et, Pr-n, Pr-i, Bu-n, Bu-i and Am-i, show that the architecture of their Cu-8(S2P)(2)S cores is fairly rigid and independent of both length and branching of the alkyl chain, and that the structure of the cluster is maintained in acetone solution. Solid- state P-31 CP-MAS and static Cu-65 NMR data for {Cu-8[S2P(O-n Pr)(2)] 6(mu(8)- S)} and {Cu-8[S2P(OEt)(2)](6) mu(8)- S)} show similarities in the icosahedral O,O'- dialkyldithiophosphate shells and in the `cubic' copper cores in these cluster compounds. The crystal structure of {Cu-8[S2P(O-n Pr)(2)](6) (mu(8)- S)} was resolved using single- crystal X- ray diffraction.
|
|
| 10. |
- Rusanova, Daniela, et al.
(författare)
-
Formation of {Cu6[S2P(OC2H5)2]6} on Cu2S Surfaces from Aqueous Solutions of the KS2P(OC2H5)2 Collector: Scanning Electron Microscopy and Solid-State 31P Cross-Polarization/Magic Angle Spinning and Static 65Cu NMR Studies
- 2005
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 21:10, s. 4420-4424
-
Tidskriftsartikel (refereegranskat)abstract
- The interactions of synthetic chalcocite surfaces with diethyldithiophosphate, potassium salt, K[S2P(OC2H5)2], were studied by means of 31P cross-polarization/magic angle spinning (CP/MAS) NMR spectroscopy and scanning electron microscopy (SEM). To identify the species formed on the Cu2S surfaces, a polycrystalline {CuI6[S2P(OC2H5)2]6} cluster was synthesized and analyzed by SEM, powder X-ray diffraction techniques and solid-state 31P CP/MAS NMR and static 65Cu NMR spectroscopy. 31P chemical shift anisotropy (CSA) parameters, CS and CS, were estimated and used for assigning the bridging type of diethyldithiophosphate ligands in the {CuI6[S2P(OC2H5)2]6} cluster. The latter data were compared to 31P CSA parameters estimated from the spinning sideband patterns in 31P NMR spectra of the collector-treated mineral surfaces: formation of polycrystalline {CuI6[S2P(OC2H5)2]6} on the Cu2S surfaces is suggested. The second-order quadrupolar line shape of 65Cu was simulated, and the NMR interaction parameters, CQ and Q, for the copper(I) diethyldithiophosphate cluster were obtained.
|
|
