Open Access
Antibacterial performance of Co-Zn ferrite nanoparticles under visible light irradiation
(Wiley, 2024-11-20) Gubieda, Alicia G.; Abad Díaz de Cerio, Ana; García-Prieto, Ana; Fernández-Gubieda, María Luisa; Cervera Gabalda, Laura María; Ordoqui Huesa, Eduardo; Cornejo Ibergallartu, Alfonso; Gómez Polo, Cristina; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2
BACKGROUND: To address water scarcity and promote sustainable resource management, more efficient and cost-effective water treatment solutions are necessary. Particularly, pathogens in drinking water are a topic of growing concern. One promising technology is the use of photocatalytic nanoparticles activated by visible light as antibacterial agents. This study focuses on the characterization and antibacterial properties of Co-Zn ferrite nanocatalysts, tested against Escherichia coli. RESULTS: The CoxZn1¿xFe2O4 (x = 0, 0.1, 0.4 and 0.6) ferrites were synthesized by the co-precipitation method. Structural, morphological and optical analyses confirmed that these nanoparticles have a cubic spinel structure, with sizes of around 10 nm, and band gap energies suitable for visible light activation (1.4¿1.7 eV). The antibacterial efficacy of the nanoparticles against E. coli was tested and compared with their photocatalytic performance employing phenol as organic pollutant model (highest phenol degradation for x = 0.6). Specifically, the antibacterial capacity of these nanoparticles was evaluated by comparing the ability of bacteria to grow after being incubated with the nanoparticles under visible light and in the dark. It was found that nanoparticles with lower cobalt content (x = 0 and 0.1) significantly reduced bacterial culturability under visible light. Transmission Electron Microscopy analysis revealed that nanoparticles with cobalt content caused bacteria to secrete biofilm, potentially offering some protection against the nanoparticles. CONCLUSION: ZnFe2O4 nanoparticles show the highest antibacterial effect amongst those tested. This is attributed to the combined action of Zn2+ ion release and the photocatalytic effect under visible light. Furthermore, Zn might inhibit protective biofilm secretion, leading to higher antibacterial effects.
Open Access
Tryptophan levels as a marker of auxins and nitric oxide signaling
(MDPI, 2022) López Gómez, Pedro; Smith, Edward N.; Bota, Pedro; Cornejo Ibergallartu, Alfonso; Urra Rodríguez, Marina; Buezo Bravo, Javier; Morán Juez, José Fernando; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Institute for Multidisciplinary Research in Applied Biology - IMAB; Ciencias; Gobierno de Navarra / Nafarroako Gobernua; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
The aromatic amino acid tryptophan is the main precursor for indole-3-acetic acid (IAA), which involves various parallel routes in plants, with indole-3-acetaldoxime (IAOx) being one of the most common intermediates. Auxin signaling is well known to interact with free radical nitric oxide (NO) to perform a more complex effect, including the regulation of root organogenesis and nitrogen nutrition. To fathom the link between IAA and NO, we use a metabolomic approach to analyze the contents of low-molecular-mass molecules in cultured cells of Arabidopsis thaliana after the application of S-nitrosoglutathione (GSNO), an NO donor or IAOx. We separated the crude extracts of the plant cells through ion-exchange columns, and subsequent fractions were analyzed by gas chromatography-mass spectrometry (GC-MS), thus identifying 26 compounds. A principal component analysis (PCA) was performed on N-metabolism-related compounds, as classified by the Kyoto Encyclopedia of Genes and Genomes (KEGG). The differences observed between controls and treatments are mainly explained by the differences in Trp contents, which are much higher in controls. Thus, the Trp is a shared response in both auxin- and NO-mediated signaling, evidencing some common signaling mechanism to both GSNO and IAOx. The differences in the low-molecularmass- identified compounds between GSNO- and IAOx-treated cells are mainly explained by their concentrations in benzenepropanoic acid, which is highly associated with IAA levels, and salicylic acid, which is related to glutathione. These results show that the contents in Trp can be a marker for the study of auxin and NO signaling.
Open Access
Effects of polyols at low concentration on the release of sweet aroma compounds in model soda beverages
(Elsevier, 2024) Barba González-Albo, Carmen; Angós Iturgaiz, Ignacio; Maté Caballero, Juan Ignacio; Cornejo Ibergallartu, Alfonso; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
This study investigated the effect of polyols erythritol, D-mannitol, and maltitol on the volatility of aroma compounds γ-butyrolactone, 3-methyl-1-butanol, and 2-phenylethanol in aqueous solution. Headspace solidphase microextraction/gas chromatography and diffusion-ordered nuclear magnetic resonance techniques were used to obtain information on aroma–food matrix interaction. Results demonstrated that adding polyols at final low concentrations of 5% or 10% (w/w) to an aqueous solution of 2-phenylethanol reduced the release of vapor-phase aromas, except in the case of 3-methyl-1-butanol, which was not affected by the presence of polyols in the liquid matrix. Polyols also reduced the diffusion coefficients of all three aroma compounds, probably due to friction between the molecules. At low polyol concentrations, aroma compound volatility and diffusion coefficient values were altered compared to those of aromas released from pure water. This observation is related to the physicochemical properties of the aroma compounds. These insights may help guide the use of the combination of aroma compounds and polyols in the formulation of sugar-free and reduced-sugar beverages. Chemical compounds: γ-butyrolactone (PubChem CID: 7302), 3-methyl-1-butanol (PubChem CID: 31260), 2-phenylethanol (PubChem CID: 6054), erythritol (PubChem CID: 222285), D-mannitol (PubChem CID: 6251), maltitol (PubChem CID: 493591).
Open Access
Pretreatment and enzymatic hydrolysis for the efficient production of glucose and furfural from wheat straw, pine and poplar chips
(Elsevier, 2019) Cornejo Ibergallartu, Alfonso; Alegría Dallo, Irantzu; García Yoldi, Íñigo; Sarobe Martínez, Íñigo; Sánchez, David; Otazu, Eduardo; Funcia, Ibai; Gil Idoate, María José; Martínez Merino, Víctor; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias; Gobierno de Navarra / Nafarroako Gobernua
A flexible approach to a two-step biorefinery for the production of glucose and furfural from three different feedstocks is presented. Pretreatment conditions were selected to drive the production towards the generation of glucose or furfural. Harsh pretreatment conditions produced solids with highly accessible glycan contents for the enzymatic hydrolysis with 100% glucose yields when wheat straw or poplar chips were used as feedstock. Mild conditions afforded xylan-rich hydrolysates that could be efficiently transformed to furfural, either under conventional or microwave heating in biphasic media. Yields for the transformation of xylan from feedstocks ranged between 45% and 90% depending on the feedstock, the thermal pretreatment and the cyclodehydration conditions. Up to 12.6 kg of glucose and materials and 2.5 kg of furfural can be produced starting from 50 kg of biomass. A new analytical methodology based on 13C NMR that provided good quality analytical results is also presented.
Open Access
Kinetics of the acid-catalyzed hydrolysis of tetraethoxysilane (TEOS) by 29Si NMR spectroscopy and mathematical modeling
(Springer, 2018) Echeverría Morrás, Jesús; Moriones Jiménez, Paula; Arzamendi Manterola, Gurutze; Garrido Segovia, Julián José; Gil Idoate, María José; Cornejo Ibergallartu, Alfonso; Martínez Merino, Víctor; Química Aplicada; Kimika Aplikatua; Institute for Advanced Materials and Mathematics - INAMAT2
Tetraethoxysilane (TEOS) is widely used to synthesize siliceous material by the sol–gel process. However, there is still some disagreement about the nature of the limiting step in the hydrolysis and condensation reactions. The goal of this research was to measure the variation in the concentration of intermediates formed in the acid-catalyzed hydrolysis by 29Si NMR spectroscopy, to model the reactions, and to obtain the rate constants and the activation energy for the hydrolysis and early condensation steps. We studied the kinetics of TEOS between pH 3.8 and 4.4, and four temperature values in the range of 277.2–313.2 K, with a TEOS:ethanol:water molar ratio of 1:30:20. Both hydrolysis and the condensation rate speeded up with the temperature and the concentration of oxonium ions. The kinetic constants for hydrolysis reactions increased in each step kh1 < kh2 < kh3 < kh4, but the condensation rate was lower for dimer formation than for the formation of the fully hydrolyzed Si(OH)4. The system was described according to 13 parameters: six of them for the kinetic constants estimated at 298.2 K, six to the activation energies, and one to the equilibrium constant for the fourth hydrolysis. The mathematical model shows a steady increase in the activation energy from 34.5 kJ mol−1 for the first hydrolysis to 39.2 kJ mol−1 in the last step. The activation energy for the condensation reaction from Si(OH)4 was ca. 10 kJ mol−1 higher than the largest activation energy in the hydrolytic reactions. The decrease in the net positive charge on the Si atom contributes to the protonation of the ethoxy group and makes it a better leaving group.
Open Access
Comprehensive kinetics of hydrolysis of organotriethoxysilanes by 29Si NMR
(American Chemical Society, 2019) Moriones Jiménez, Paula; Arzamendi Manterola, Gurutze; Cornejo Ibergallartu, Alfonso; Garrido Segovia, Julián José; Echeverría Morrás, Jesús; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2
The kinetics of several representative hybrid precursors were studied via 29Si NMR: three alkyl precursors, methyltriethoxysilane, ethyltriethoxysilane, and propyltriethoxysilane; as well as two unsaturated radicals, vinyltriethoxysilane and phenyltriethoxysilane. The reaction rate is related to the chemical shift of 29Si in the NMR spectra, which gives information about the electronic density of the Si atoms and the inductive effects of substituents. The concentration of the precursors decreased exponentially with time, and the intermediate products of hydrolysis and the beginning of the condensation reactions showed curves characteristic of sequential reactions, with a similar distribution of the species as a function of the fractional conversion. For all of the precursors, condensation started when the most hydrolyzed species reached a maximum concentration of 0.30 M, when the precursor had run out. A prediction following the developed mathematical model fits the experimental results in line with a common pathway described by eight parameters.
Open Access
IAOx induces the SUR phenotype and differential signalling from IAA under different types of nitrogen nutrition in Medicago truncatula roots
(Elsevier, 2019) Buezo Bravo, Javier; Esteban Terradillos, Raquel; Cornejo Ibergallartu, Alfonso; López Gómez, Pedro; Marino Bilbao, Daniel; Chamizo Ampudia, Alejandro; Gil Idoate, María José; Martínez Merino, Víctor; Morán Juez, José Fernando; Zientziak; Institute for Multidisciplinary Research in Applied Biology - IMAB; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Indole-3-acetaldoxime (IAOx) is a particularly relevant molecule as an intermediate in the pathway for tryptophan-dependent auxin biosynthesis. The role of IAOx in growth-signalling and root phenotype is poorly studied in cruciferous plants and mostly unknown in non-cruciferous plants. We synthesized IAOx and applied it to M. truncatula plants grown axenically with NO3-, NH4+ or urea as the sole nitrogen source. During 14 days of growth, we demonstrated that IAOx induced an increase in the number of lateral roots, especially under NH4+ nutrition, while elongation of the main root was inhibited. This phenotype is similar to the phenotype known as “superroot” previously described in SUR1- and SUR2-defective Arabidopsis mutants. The effect of IAOx, IAA or the combination of both on the root phenotype was different and dependent on the type of N-nutrition. Our results also showed the endogenous importance of IAOx in a legume plant in relation to IAA metabolism, and suggested IAOx long-distance transport depending on the nitrogen source provided. Finally, our results point out to CYP71A as the major responsible enzymes for IAA synthesis from IAOx.
Open Access
A new oxidative pathway of nitric oxide production from oximes in plants
(Cell Press, 2024) López Gómez, Pedro; Buezo Bravo, Javier; Urra Rodríguez, Marina; Cornejo Ibergallartu, Alfonso; Esteban Terradillos, Raquel; Fernández de los Reyes, Jorge; Urarte Rodríguez, Estíbaliz; Rodríguez-Dobreva, Estefanía; Chamizo Ampudia, Alejandro; Eguaras, Alejandro; Wolf, Sebastian; Marino Bilbao, Daniel; Martínez Merino, Víctor; Morán Juez, José Fernando; Ciencias; Zientziak; Institute for Multidisciplinary Research in Applied Biology - IMAB; Institute for Advanced Materials and Mathematics - INAMAT2
Nitric oxide (NO) is an essential reactive oxygen species and a signal molecule in plants. Although several studies have proposed the occurrence of oxidative NO production, only reductive routes for NO production, such as the nitrate (NO-3) -upper-reductase pathway, have been evidenced to date in land plants. However, plants grown axenically with ammonium as the sole source of nitrogen exhibit contents of nitrite and NO3, evidencing the existence of a metabolic pathway for oxidative production of NO. We hypothesized that ox- imes, such as indole-3-acetaldoxime (IAOx), a precursor to indole-3-acetic acid, are intermediate oxidation products in NO synthesis. We detected the production of NO from IAOx and other oximes catalyzed by peroxidase (POD) enzyme using both 4-amino-5-methylamino-20,70-difluorescein fluorescence and chem- iluminescence. Flavins stimulated the reaction, while superoxide dismutase inhibited it. Interestingly, mouse NO synthase can also use IAOx to produce NO at a lower rate than POD. We provided a full mech- anism for POD-dependent NO production from IAOx consistent with the experimental data and supported by density functional theory calculations. We showed that the addition of IAOx to extracts from Medicago truncatula increased the in vitro production of NO, while in vivo supplementation of IAOx and other oximes increased the number of lateral roots, as shown for NO donors, and a more than 10-fold increase in IAOx dehydratase expression. Furthermore, we found that in vivo supplementation of IAOx increased NO pro- duction in Arabidopsis thaliana wild-type plants, while prx33-34 mutant plants, defective in POD33-34, had reduced production. Our data show that the release of NO by IAOx, as well as its auxinic effect, explain the superroot phenotype. Collectively, our study reveals that plants produce NO utilizing diverse molecules such as oximes, POD, and flavins, which are widely distributed in the plant kingdom, thus intro- ducing a long-awaited oxidative pathway to NO production in plants. This knowledge has essential impli- cations for understanding signaling in biological systems.
Open Access
Systematic diffusion-ordered spectroscopy for the selective determination of molecular weight in real lignins and fractions arising from base-catalyzed depolymerization reaction mixtures
(American Chemical Society, 2020) Cornejo Ibergallartu, Alfonso; García Yoldi, Íñigo; Galilea Gonzalo, Rebeca; Hablich Alvarracin, Karina Lissett; Gil Idoate, María José; Martínez Merino, Víctor; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias; Gobierno de Navarra / Nafarroako Gobernua
The valorization of biorefinery downstream lignin fractions is a key issue in increasing the sustainability of second-generation biofuels. The development of reliable methodologies for the selective determination of the apparent masses of the poly(hydroxy)-aromatic ethers arising from lignin depolymerization reaction is crucial. Diffusion-ordered spectroscopy (DOSY) has been tested to estimate the molecular weight in downstream biorefinery lignins and base-catalyzed depolymerization reaction mixtures. Excellent correlation was found in the calibration of molecular weight and diffusion coefficients with standards. DOSY permitted the selective estimation of the apparent masses of different fractions in the lignin and in the depolymerization reaction mixtures, providing a more profound knowledge of the reaction mixture composition than that obtained with traditional size-exclusion chromatography (SEC). Excellent correlations have been achieved in the estimation of the apparent masses of poly(hydroxy)-aromatic ethers between SEC and DOSY. This permits a reliable estimation of the molecular weight of different fractions in the lignin and in the depolymerization product, which is essential for their further applications.
Open Access
Innovative flow-through reaction system for the sustainable production of phenolic monomers from lignocellulose catalyzed by supported Mo2C
(Wiley, 2024) Maisterra Udi, Maitane; Atienza Martínez, María; Hablich Alvarracin, Karina Lissett; Moreira, Rui; Martínez Merino, Víctor; Gandía Pascual, Luis; Cornejo Ibergallartu, Alfonso; Bimbela Serrano, Fernando; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra - Nafarroako Unibertsitate Publikoa
Molybdenum carbide supported on activated carbon (β-Mo2C/AC) has been tested as catalyst in the reductive catalytic fractionation (RCF) of lignocellulosic biomass both in batch and in Flow-Through (FT) reaction systems. High phenolic monomer yields (34 wt.%) and selectivity to monomers with reduced side alkyl chains (up to 80 wt.%) could be achieved in batch in the presence of hydrogen. FT-RCF were made with no hydrogen feed, thus via transfer hydrogenation from ethanol. Similar selectivity could be attained in FT-RCF using high catalyst/biomass ratios (0.6) and high molybdenum loading (35 wt.%) in the catalyst, although selectivity decreased with lower catalyst/biomass ratios or molybdenum contents. Regardless of these parameters, high delignification of the lignocellulosic biomass and similar monomer yields were observed in the FT mode (13-15 wt.%) while preserving the holocellulose fractions in the delignified pulp. FT-RCF system outperforms the batch reaction mode in the absence of hydrogen, both in terms of activity and selectivity to reduced monomers that is attributed to the two-step non-equilibrium processes and the removal of diffusional limitations that occur in the FT mode. Even though some molybdenum leaching was detected, the catalytic performance could be maintained with negligible loss of activity or selectivity for 15 consecutive runs.