Christian David Alcívar León

Penaeus sp. shells (shrimp) were used to extract chitosan using acid and basic treatments, which were characterized by IR spectroscopy, Raman spectroscopy, potentiometric titration, and elemental analysis. The degrees of deacetylation were determined to be 71.8%, 75.6%, 53.4%, and 68.6%, respectively. Likewise, viscosimetry measurements were carried out, determining an average molecular weight of chitosan 1 of 1521467.919 (g/mol). The obtained chitosan was used as a substrate in condensation reactions with 10 para-substituted benzaldehydes. The products obtained were characterized by IR, Raman, and ¹H-NMR spectroscopy, AE (Elemental Analysis), TGA (Thermogravimetric Analysis), and DSC (Differential Scanning Calorimetry). For the obtained polymers, biological assays of cytotoxicity using RAW macrophage cells and leishmanicidal activity on promastigotes of Leishmania mexicana were performed. The results show that the synthesized products do not present in vitro cytotoxicity, and that 1 (Chitosan) and 3i (Schiff Base) present leishmanicidal activity. Selected derivatives were incorporated into polyvinyl alcohol-based films and evaluated for surface topography and gas permeability. AFM revealed nanometric roughness patterns, while gas exchange studies demonstrated selective CO₂/O₂ permeability, supporting passive modified atmosphere formation in packaged carrots. Mechanical characterization revealed that the incorporation of Schiff base derivatives significantly influences tensile strength and flexibility, with certain films exhibiting enhanced elongation and mechanical performance compared to pure PVA, highlighting their potential for packaging applications. These findings confirm that chemical functionalization enhances the versatility of chitosan, allowing the design of tailored biopolymers. The synthesized derivatives show promising characteristics for the development of biodegradable films with potential applications in food packaging and antiparasitic material development.

Chitosan is a biopolymer with excellent properties such as biodegradability, biocompatibility, bioactivity, and non-toxicity, making it an attractive material for various applications. In this study, to enhance these properties particularly for the development of food coatings chitosan derivatives (1,2,3-triazoles) were synthesized via microwave-assisted 1,3-dipolar cycloaddition (CuAAC) using different terminal alkynes. The resulting compounds were obtained in high yields 79.7–88.0% and characterized by vibrational (IR) and electronic (UV–Visible) spectroscopy. Films were formed by combining the derivatives with PVA and characterized using differential scanning calorimetry (DSC), tensile strength testing, and water vapor permeability analysis. The resulting films exhibited improved mechanical properties, homogeneous thicknesses, low-porosity surfaces, and favorable barrier properties, highlighting their potential applicability as food coating materials.

S. rosmarinus L., an aromatic species introduced to Ecuador, is valued in gastronomy and traditional medicine. Introduced plants adapt to new environments and may exhibit variations in bioactive compounds. This study evaluates the essential oil composition and antioxidant activity of rosemary from urban and rural areas. The oil extracted by microwave showed different yield (0.93% in urban and 1.02% rural) and significant variation in volatile profiles. Antioxidant activity was determined by DPPH and ABTS assays. Tetrachloroethylene was the main component, with 2.87% in urban and 13.10% in rural oil. These findings highlight rosemary’s potential as an ecological indicator of ecosystem quality.

Chitosan biopolymer membranes reinforced with channel-selective ZIF-8 nanofillers were developed and thoroughly characterized as separators for bioelectrochemical systems. This study explores the synergistic effect of incorporating ZIF-8 into a chitosan matrix to enhance membrane performance. Key properties including water retention, chemical and thermal stability, surface resistance, antifouling capacity, and ionic conductivity were evaluated and benchmarked against commercial Nafion-117 and nanofiltration (NF) membranes. The ZIF-8/chitosan composite membranes (ZIF-8/CS) demonstrated excellent water retention and structural stability under harsh conditions, along with significantly reduced surface resistance and effective rejection of organic contaminants and salts (NaCl, Na₂SO₄). Notably, the composite ZIF-8/CS membranes achieved an ionic conductivity of 0.099 S/cm, approaching the value of Nafion-117 (0.13 S/cm) and substantially surpassing that of the NF membrane (0.013 S/cm). These results indicate that ZIF-8-reinforced chitosan membranes present a promising, sustainable, and cost-effective alternative to traditional separators in bioelectrochemical applications.

Bioelectrochemical systems (BESs) are technologies capable of converting chemical energy into electrical energy or producing value-added compounds. These systems typically employ Nafion membranes as proton exchange separators; however, Nafion is costly and prone to fouling. In this study, mixed-matrix membranes (MMMs) based on chitosan and its derivatives, incorporated with Er- and Al-doped ZnO nanoparticles, were synthesized and evaluated. Key properties assessed included antimicrobial activity, antifouling behavior, chemical stability, water retention, and proton conductivity. The results demonstrated that the chitosan-based membranes doped with Er/Al/ZnO outperformed Nafion in terms of antifouling properties, water retention, and a protective effect on the surface of the membrane against Escherichia coli and Staphylococcus aureus, while exhibiting comparable proton conductivity and chemical stability.

Los residuos orgánicos más comunes en Ecuador incluyen cáscaras de diversas frutas, entre las cuales destaca la cáscara de las distintas variedades de plátano, que contienen una gran cantidad de nutrientes esenciales con potencial para ser aprovechados en diferentes campos científicos. El objetivo de este estudio fue caracterizar fisicoquímicamente y evaluar las actividades microbiológicas, antioxidante y antimicrobiana, de cáscaras de maqueños (Musa balbisiana) cultivados en tres localidades del Ecuador: Napo, Quevedo y Zamora. Los análisis fisicoquímicos revelaron valores promedio de humedad (7,74 ± 0,41 %), ceniza (13,00 ± 0,42 %), grasa (5,57 ± 0,81 %), proteína (5,99 ± 1,05 %), fibra (9,81 ± 1,26 %) y carbohidratos (65,90 ± 2,78 %). La evaluación de la capacidad antioxidante, los polifenoles totales y la actividad antimicrobiana se realizó en extractos etanólicos al 60 y 80 %. El contenido de polifenoles totales, determinado mediante el método de Folin-Ciocalteu, mostró el valor más alto en la muestra de Zamora extraída con etanol al 60 %, con 72,63 ± 0,98 mg equivalentes de ácido gálico/100 g de muestra seca. La capacidad antioxidante, evaluada mediante el método DPPH, registró su máximo valor en la muestra de Zamora extraída con etanol al 80 %, con 255,92 ± 1,04 μmol equivalentes de trolox/100 g de peso seco. En cuanto a la actividad antimicrobiana, para Staphylococcus aureus se observaron halos de inhibición de 10 mm en Napo, 7 mm en Quevedo y 12 mm en Zamora con etanol al 80 %, mientras que con etanol al 60 % los halos fueron de 8 mm en las tres localidades. Para Bacillus cereus, la concentración del 80 % mostró halos de 8 mm en Napo, 6 mm en Quevedo y 9 mm en Zamora, mientras que con etanol al 60 % solo se detectó actividad inhibitoria en Quevedo (8 mm). No se observó inhibición para Escherichia coli en ninguno de los extractos evaluados. Estos resultados indican que la eficacia antimicrobiana varía según la concentración del solvente y el tipo de microorganismo, siendo S. aureus el más susceptible bajo las condiciones evaluadas. La caracterización realizada sugiere que los residuos de maqueño podrían ser utilizados como materiales base, abriendo posibilidades para optimizar el aprovechamiento de estos subproductos agroindustriales en diversas aplicaciones.

Chitosan biopolymer membranes reinforced with channel-selective ZIF-8 nanofillers were developed and characterized for use as separators in bioelectrochemical systems. The study focused on the application of biopolymer chitosan in combination with ZIF-8 as nano reinforcement agents to improve membrane performance. Key properties such as water retention, chemical and thermal stability, surface resistance, antifouling ability, and ionic conductivity of the mixed matrix membranes (Composite ZIF-8/chitosan) were evaluated and compared with commercial Nafion-117 and nanofiltration (NF) membranes. The composite ZIF-8/chitosan membranes exhibited excellent water retention and structural stability under harsh conditions, while reducing surface resistance and effectively rejecting organic contaminants and salts (NaCl, Na₂SO₄). Impressively, the ionic conductivity reached 0.105 S/cm, which is similar to that of Nafion-117. These results suggest that biopolymer chitosan reinforced with ZIF-8 nanofillers offers a sustainable and cost-effective alternative for use as separators in bioelectrochemical systems applications.

El uso descontrolado de empaques alimenticios, y la ineficiencia de procesos de reciclaje han despertado el interés en la búsqueda de macromoléculas derivadas de fuentes naturales como reemplazo de los plásticos actuales. En este sentido, se desarrolló la síntesis de derivados de quitosano a partir de reacciones de Química Click, utilizando quitosano extraído de exoesqueletos de camarón. Los derivados de 1, 2, 3 triazol-quitosano se obtuvieron mediante reacciones de cicloadición azida-alquino asistidas por ultrasonido sobre una matriz de quitosano de peso molecular medio de 453 kDa, y un grado de desacetilación mayor al 90%. Se realizaron ensayos de actividad antimicrobiana frente a S. aureus, K. pneumoniae, P. aeruginosa, E. coli y S. typhimurium en concentraciones de 1% y 2%, se observó actividad antimicrobiana de todos los derivados, con halos de inhibición iguales o superiores a gentamicina. Asimismo, se desarrollaron películas de cada derivado utilizando PVA como plastificante. La resistencia a la tracción de las películas estuvo entre 42 MPa y 68 MPa, siendo mayores al valor obtenido para un plástico de empaque común, 41 MPa. Los ensayos de DSC evidenciaron la estabilidad térmica del quitosano y sus derivados, y permitieron determinar sus temperaturas de transición vítrea. Se realizaron medidas de AFM de las películas, la rugosidad mostro micro superficies homogéneas. Por lo tanto, las películas con derivados de 1, 2, 3 triazol-quitosano presentaron características mecánicas mejoradas, actividad antimicrobiana, temperaturas elevadas de transición vítrea y rugosidad uniforme a nivel micrométrico que le brindan potencial aplicación para el desarrollo de empaques alimenticios.

A study of the solid-state intermolecular interactions of twenty-nine benzopyrans substituted with polyhaloalkyl groups was carried out by quantum chemical calculations using the Mercury and WinGX computer programs. Molecular structures were obtained from crystallographic information files (CIF) of the CCDC database. C-H—O, C-H—X, C-X—O and C-X—X type contacts, characterized as unconventional hydrogen bonds, were identified and calculated. The criteria used for distances and angles were d(D—A) < R(D) + R(A) + 0.50 and d(H—A) < R(H) + R(A)—0.12°, where D-H—A > 100.0°. D is the donor atom, A is the acceptor atom, R is the Van der Waals radius and d is the interatomic distance. In addition, Etter’s notation was used to describe sets of hydrogen bonds in organic crystals, detailing the intermolecular contacts and periodic arrangements of the crystal packing. It was corroborated that certain positions of halogen atoms and their interactions play an important role in stabilizing the crystal lattice.

Bioelectrochemical systems are energy-efficient devices that transform chemical energy into electrical energy or synthesize products of interest. These technologies make use of Nafion membranes that function as proton exchangers; however, these separators have some problems, such as fouling. Therefore, this research explores mixed-matrix membranes of chitosan and chitosan derivatives to determine their antimicrobial, anti-fouling, chemical stability and high-water retention properties. The results showed that these membranes could be good candidates to be used as separators in bioelectrochemical systems.