Ana Estela Ledesma

The rapid characterization of lactic acid bacteria (LAB) with probiotic and technological properties is crucial for functional food design. In this study, fourteen LAB strains belonging to the species Lactiplantibacillus (L.) plantarum, Lentilactobacillus (L.) parabuchneri, and Leuconostoc (L.) mesenteroides were differentiated using Raman spectroscopy. By integrating Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA), we achieved a clear inter-generic separation while simultaneously enabling the intra-specific grouping of L. plantarum strains. Our results demonstrate that the Raman spectral fingerprint, coupled with supervised chemometric models, successfully categorized the strains into three distinct clusters based on their macromolecular profiles. Specifically, the analysis provided high-resolution differentiation between genera and, more importantly, allowed for the fine-scale clustering of diverse L. plantarum isolates. This highlights Raman spectroscopy as a robust, non-destructive tool for the rapid identification and taxonomic classification of LAB, offering a high-throughput alternative to traditional molecular methods for strain-level discrimination.

El presente estudio se centró en la calidad del agua del río Dulce, provincia de Santiago del Estero, Argentina, de vital importancia para la región, que provee agua para consumo humano y para el sistema de riego agrícola. Se realizaron muestreos en mayo, junio, julio, septiembre, noviembre y diciembre, en el área de un dique derivador. Se analizaron parámetros básicos, iones mayoritarios, nutrientes y el comportamiento de la materia orgánica disuelta cromofórica (MODC) y se diagnosticó la aptitud para riego y consumo. Los resultados indicaron aguas de carácter alcalino, con elevada mineralización y predominio de sodio (Na⁺) y cloruro (Cl⁻). Hidroquímicamente, se identifican como aguas cloruradas sulfatadas sódicas. Fuertes variaciones estacionales se asocian al régimen hidrológico y las condiciones climáticas, con aumento en la conductividad eléctrica y concentración de sales durante la estación seca. Se detectaron concentraciones de nitratos y fosfatos elevadas, lo que evidencia influencia antropogénica vinculada a actividades contaminantes. Los parámetros fisicoquímicos fueron aceptables para consumo humano según los estándares de la OMS y el CAA, mientras para riego presenta riesgo de salinización. La variación de la MODC sugiere cambios en las fuentes y reactividad de la materia orgánica en función del ciclo hidrológico, con ingreso de materiales alóctonos (suelos y material vegetal fresco) durante la temporada húmeda e incremento de origen autóctono (productividad primaria y degradación de materiales orgánicos) durante los caudales bajos. En conclusión, el río Dulce presenta una composición química controlada principalmente por factores naturales, aunque con evidencias de aportes antropogénicos.

Goat milk can be a vehicle for beneficial microorganisms, such as probiotic lactic acid bacteria (LAB). During lactic fermentation, the hydrolysis of milk proteins can improve their nutritional properties and sensory attributes and even have beneficial health effects. The objective of this study was to evaluate the caseinolytic activity of LAB strains with probiotic potential and to monitor the changes induced by fermentation and during storage in milk components using Fourier transform infrared (FTIR) spectroscopy. First, the proteolytic activity of 36 LAB strains isolated from dairy products was qualitatively assessed. Then, 17 strains with probiotic potential and moderate to high proteolytic activity were selected for further analysis. Casein proteolysis was found to be strain-dependent, with a decrease in total protein concentration ranging from 28% to 87% and an increase in amino acids ranging from 29% to 88%. Furthermore, a notable difference was observed in the amide bands in the FTIR spectra between the beginning and end of incubation, showing a decrease in the intensities of the bands attributed to proteins. In fermented goat milk, LAB growth resulted in a final count between 0.62 and 2.6 log CFU/mL, a 0.29 to 2.0 drop in pH, and lactic acid production between 0.20 and 1 g/L. FTIR spectra revealed time-dependent modifications in amide I and II bands accompanied by a marked reduction in carbohydrate content and an increase in lactic acid signal. After 21 days of storage, the viability of the strains, pH, and lactic acid in the fermented milks were not substantially modified. These results highlight the potential of lactic fermentation with strains selected for their probiotic potential as an approach to producing value-added goat milk products, as well as the usefulness of FTIR spectroscopy for characterizing complex systems such as goat milk.

Postharvest fungal diseases are the main cause of economic losses in lemon production. The continued use of synthetic fungicides to control the diseases favors the emergence of resistant strains, which encourages the search for alternatives. The aim of this study was to assess the efficacy of metallic nanoparticles (NPs) as antifungal agents against local isolates of Penicillium digitatum and Penicillium italicum, each of them in a fungicide-sensitive and -resistant version, and a Geotrichum citri-aurantii isolate. NPs of ZnO, CuO, and Ag were synthesized and characterized by spectroscopy and microscopy, presenting average sizes < 25 nm and spherical shapes. ZnO-NPs did not present antifungal activity at the assayed conditions, while the minimum fungicidal concentrations (MFCs) were 1000 and 10 µg mL⁻¹ for CuO-NPs and Ag-NPs, respectively. The NPs’ antimicrobial action included conidial membrane permeability and strong intracellular disorganization. Moreover, the Ag-NPs reduced green mold incidence on inoculated lemons when applied to the fruit. Taken together, Ag-NPs were effective in inhibiting both fungicide-sensitive and -resistant isolates of the main lemon postharvest pathogens, suggesting their potential use as an alternative approach.

Bile acids (BAs) are the main endogenous modulators of the composition and metabolic activity of the intestinal microbiota. In the present work, the effect of conjugated (glycodeoxycholic, glycocholic, taurodeoxycholic, taurocholic acids) and free BAs [cholic acid (CA) and deoxycholic acid (DCA)] on the survival, biological molecules, and structural and surface properties of two potential probiotic lactic acid bacteria (LAB) was evaluated. For this, viability assays, Raman spectroscopy, scanning electron microscopy (SEM), and zeta potential (ZP) measurements were employed. Our results evidenced that free BAs were more toxic than conjugates, with CA being significantly more harmful than deoxycholic acid (DCA). RAMAN studies show that BAs modify the bands corresponding to proteins, lipids, carbohydrates, and DNA. SEM showed that BAs cause surface distortions with depressions and fold formation, as well as incomplete cell division. DCA was the one that least altered the ZP of bacteria when compared to CA and taurodeoxycholic acid, with gradual changes towards more positive values. In general, the magnitude of these effects was different according to the BA and its concentration, being more evident in the presence of CA, even at low concentrations, which would explain its greater inhibitory effect. This work provides solid evidence on the effects of BAs on LAB that will allow for the development of strategies by which to modulate the composition of the microbiota positively.

The ever-expanding pandemic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has gained attention as COVID-19 and caused an emergency in public health to an unmatched level to date. However, the treatments used are the only options; currently, no effective and licensed medications are available to combat disease transmission, necessitating further research. In the present study, an in silico-based virtual screening of anti-HIV bioactive compounds from medicinal plants was carried out through molecular docking against the main protease (M^pro) (PDB: 6LU7) of SARS-CoV-2, which is a key enzyme responsible for virus replication. A total of 16 anti-HIV compounds were found to have a binding affinity greater than −8.9 kcal/mol out of 150 compounds screened. Pseudohypericin had a high affinity with the energy of −10.2 kcal/mol, demonstrating amino acid residual interactions with LEU141, GLU166, ARG188, and GLN192, followed by Hypericin (−10.1 kcal/mol). Moreover, the ADME (Absorption, Distribution, Metabolism and Excretion) analysis of Pseudohypericin and Hypericin recorded a low bioavailability (BA) score of 0.17 and violated Lipinski’s rule of drug-likeness. The docking and molecular simulations indicated that the quinone compound, Pseudohypericin, could be tested in vitro and in vivo as potent molecules against COVID-19 disease prior to clinical trials.This was also supported by the theoretical and computational studies conducted. The global and local descriptors, which are the underpinnings of Conceptual Density FunctionalTheory (CDFT) have beenpredicted through successful model chemistry, hoping that they could be of help in the comprehension of the chemical reactivity properties of the molecular systems considered in this study.

Amylase is an enzyme exposed to the effect of bile acids (BAs) in intestine. BAs may potential reduce the activity of the enzyme. In this paper, an insight in biophysical and structural terms on how taurodeoxycholic and deoxycholic acids (TDCA and DCA, respectively) interact with α‐amylase is given, using UV‐visible, fluorescence and infrared spectroscopy (FTIR), electron microscopy, dynamic light scattering (DLS) and molecular docking calculations. Fluorescence spectroscopy measurements, confirm that TDCA and DCA interact with α‐amylase with high affinity causing conformational changes. Also, DCA significantly modify the thermal denaturation of the protein. Besides, DCA induces a decrease in α‐helix and unordered region, together with an important increase in β‐sheet, modifying the surface charges of the protein and inducing the formation of protein aggregates producing a loss of activity. Docking results indicate that TDCA interacts with the surface of the enzyme, while DCA may stabilize inside the active site of α‐amylase thereby justifying its inhibitory mechanism. BAs acts as protein‐unfolding agents and the mechanism is dependent on the structure of the bile acid under study. These findings provide a deeper understanding of the interaction of BAs with proteins and its role as protein‐unfolding agents, at molecular level.

N-methylcytisine alkaloid was fully characterised by FTIR and ultraviolet spectroscopies. Two structures of this alkaloid that change the position of carbonyl groups, called C1 and C2, were theoretically analysed in both the gas phase and water solution at the B3LYP/6-311++G** level of theory. The dipole moment values of this molecule increase in the solution. The structural properties of N-methylcytisine were analysed to investigate its conformational preference given in natural sources. Then, Mulliken, MK and NPA charges with bond orders, natural bond orbital, molecular electrostatic potentials and topological properties expose a higher stability of this molecule in water solution. The frontier orbital analysis justifies the blue and red colourations observed in the mapped surfaces corresponding to electron density. Very good agreements with experimental data are observed for C2 in both ¹H- and ¹³C-NMR spectra and their presence was supported by the ultraviolet spectra. For the first time, a complete assignment of infrared bands and force constants of N-methylcytisine in both media are reported as the scaled frequencies are in agreement with those experimentals. Molecular docking studies were used to predict the biological activity, which evidenced that N-methylcytisine alkaloid can act as partial agonist of nicotinic acetylcholine receptors. GRAPHICAL ABSTRACT