RESUMEN

Bacteriocins are antimicrobial compounds that have awakened interest across several industries due to their effectiveness. However, their large-scale production often becomes unfeasible on an industrial scale, primarily because of high process costs. Addressing this challenge, this work analyzes the potential of using low-cost whey permeate powder, without any supplementation, to produce bacteriocin-like inhibitory substances (BLIS) through the fermentation of Latilactobacillus sakei. For this purpose, different concentrations of whey permeate powder (55.15 gL-1, 41.3 gL-1 and 27.5 gL-1) were used. The ability of L. sakei to produce BLIS was evaluated, as well as the potential of crude cell-free supernatant to act as a preservative. Raman spectroscopy and surface-enhanced Raman scattering (SERS) provided detailed insights into the composition and changes occurring during fermentation. SERS, in particular, enhanced peak definition significantly, allowing for the identification of key components, such as lactose, proteins, and phenylalanine, which are crucial in understanding the fermentation process and BLIS characteristics. The results revealed that the concentration of 55.15 gL-1 of whey permeate powder, in flasks without agitation and a culture temperature of 32.5 °C, presented the highest biological activity of BLIS, reaching 99% of inhibition of Escherichia coli and Staphylococcus aureus with minimum inhibitory concentration of 36-45%, respectively. BLIS production began within 60 h of cultivation and was associated with class II bacteriocins. The results demonstrate a promising approach for producing BLIS in an economical and environmentally sustainable manner, with potential implications for various industries.

Asunto(s)

Antibacterianos , Bacteriocinas , Latilactobacillus sakei , Espectrometría Raman , Suero Lácteo , Suero Lácteo/química , Bacteriocinas/biosíntesis , Bacteriocinas/farmacología , Antibacterianos/farmacología , Antibacterianos/biosíntesis , Antibacterianos/química , Latilactobacillus sakei/metabolismo , Polvos , Fermentación

RESUMEN

CONTEXT: Triazene compounds (-NNN(H)-) exhibit versatility in biological, physical, and chemical applications. In their anionic form (-NNN-)(-), they can act as coordinating sites for metals, forming metallic complexes. In this study, two new isomeric triazene compounds with meta- and para-substituents in their neutral and anionic forms were investigated. A combination of detailed experimental spectroscopic characterization and computational chemistry analyses were employed. The new compounds, 1-(2-benzamide)-3-(3-nitrophenyl) triazene (m-TZN) and 1-(2-benzamide)-3-(4-nitrophenyl) triazene (p-TZN), were compared to 1,3-diphenyltriazene (dph-TZN) to understand the effects of functionalization and targeted triazene deprotonation. The anionic forms are stable, and our investigation suggests that these new compounds are suitable tridentate ligands that can act as chelating agents for metallic cations in stable complexes, similar to those found in vitamin B12. METHODS: The absorption, vibrational, and electronic properties of the newly synthesized triazene compounds were extensively characterized using FT-IR/FT-Raman and UV-Vis spectroscopy. Their distinct molecular properties, intramolecular hydrogen bond effects, stability, and electronic transitions were investigated using the ORCA software. These analyses involved DFT and TD-DFT calculations at the ωB97X-D3/Def2-TZVP level of theory with THF CPCM implicit solvation to determine the molecular topology and electronic structure. The advanced STEOM-DLPNO-CCSD method for excited states was employed, enabling an in-depth analysis of ground and excited-state chemistry, accounting for precise electronic correlation and solvation effects. Explicit THF solvation was tested on the full TD-DFT ωB97X-D3/Def2-TZVP level and using ONIOM on the STEOM calculation. Reactivity was studied using Fukui functions, and action as chelating agents was investigated using GFN-xTB2 and DFT.

RESUMEN

Zinc titanates are compounds that have shown great application versatility, including in the field of semiconductors. Solid state reactions, the polymeric precursor method and the hydrothermal method are the most mentioned synthesis of these compounds in the literature. In the present work, we use microwave assisted hydrothermal method (MAH) to synthesize zinc titanate and evaluate its potential for solar cell applications through structural and optical characterization techniques. The synthesized samples were also subjected to a variable temperature heat treatment in the range of 500 °C-800 °C. The analysis showed that the crystallization of the material starts at 500 °C and that samples submitted to temperatures of 600 °C-800 °C showed the formation of two phases of zinc titanates, being a cubic phase of ZnTiO3, considered rare in the literature, predominant up to a temperature of 800 °C. The optical characterization, based on the techniques of photoluminescence spectroscopy and UV-Visible spectroscopy, showed that the photoluminescent activity and the energy of the band gap increased with the increase of the temperature of the heat treatment, having the highest response in 700 °C, facts that can be linked to the predominant formation of the cubic phase of ZnTiO3 and simultaneous of the cubic and rhombohedral phases of ZnTiO3 at 700 and 800 °C. Finally, we highlight as the most important results, the fact that it was possible to obtain these titanates at a temperature lower than that reported in the literature, and that the heat-treated sample at 500 °C is the one with the lowest energy expenditure to be synthesized and the one with the greatest potential for application in dye-sensitized solar cells (DSSC's).

RESUMEN

Benzothiazole derivatives were used as models to study the excited-state intramolecular proton transfer (ESIPT) from an experimental and theoretical point of view. The experimental electronic and vibrational results were compared with a comprehensive selection of state-of-the-art computational methods in a workflow approach. The latter were performed based on modern techniques, such as DLPNO-CCSD(T), which gives the reference energies and current methodologies for ESIPT analysis, such as molecular dynamics and charge density difference testing. The theoretical vibrational results were focused on the stretch vibrational-mode of the hydroxyl group, which indicated a large increase in the intramolecular hydrogen bond strength, which facilitates the ESIPT process. Theoretically, the optimization of a large number of molecules shows that π-stacking plays a fundamental role in benzothiazole stabilization, with a remarkably strong intramolecular hydrogen bond. The potential energy surface of the ESIPT reactive benzothiazole (4HBS) has a clear transition state where ESIPT is easily observed with a large difference in energy between the enol and keto tautomer. Additionally, molecular dynamics showed that the ESIPT process occurs very fast. The tautomer appears around 8.7 fs and the enolic form is regenerated in just 24 fs, closing the Förster cycle. The calculated Stokes shift could be related to the ESIPT process and the experimental solid-state emission spectrum matched almost perfectly with the theoretical one. In contrast, for the non-ESIPT benzothiazole (4HBSN), the agreement between theory and experiment was limited, probably due to intermolecular interaction effects that are not considered in these calculations.