Noé Luiz-Santos

The increasing prevalence of antimicrobial resistance in bacteria highlights the need for alternative membrane-active compounds with favorable safety profiles. β-Caryophyllene (BCP), a bicyclic sesquiterpene, has demonstrated antimicrobial effects; however, its biological responses in Gram-negative bacteria and associated membrane interactions remain insufficiently characterized. In this study, the growth inhibitory effect of BCP against E. coli ATCC 25922 was evaluated through OD595 growth kinetics, while hemocompatibility was assessed using sheep erythrocytes, and cannabidiol (CBD) was included as a comparative control. To investigate membrane-associated effects, differential scanning calorimetry (DSC) was performed using DPPE/DPPG (8:2) bilayers as a simplified phospholipid membrane model. BCP inhibited bacterial growth with an IC₅₀ of 0.83 mg/mL and exhibited low hemolytic activity (2.92% at 1 mg/mL). DSC analyses revealed concentration-dependent shifts in phase transition temperature and reductions in transition enthalpy (ΔH kJ/mol) 36% and 82% for BCP-5 and CBD-10 according to the control, indicating alterations in lipid organization and membrane thermotropic behavior. In contrast, CBD showed greater growth inhibitory potency (IC₅₀ of 0.042 mg/mL) but more pronounced disruption of membrane organization. Overall, these findings suggest that BCP exhibits moderate growth inhibition associated with membrane related effects and low hemolytic activity, providing insights into the relationship between physicochemical properties, membrane interactions, and biological responses.

El objetivo de este estudio fue determinar el efecto de la celobiosa al 1% como fuente principal de carbono en un cultivo MRS de Limosilactobacillus reuteri, formulado para la biotransformación de glicerol a 3-hidroxipropionaldehído, un agente antimicrobiano de amplio espectro. Se utilizó Escherichia coli O157:H7 como organismo modelo para evaluar el efecto de la inhibición bacteriana. Un segundo caldo MRS formulado con 1% de glucosa y un caldo MRS comercial estándar fueron utilizados como comparativos. El 3-HPA utilizado fue producido durante la fase exponencial de crecimiento (2 a 12 horas) de cada cultivo MRS. El 3-HPA producido en los medios con celobiosa y MRS comercial inhibió 45.01 ± 18.51% y un 35.94 ± 7.76% (p>0.05) respectivamente el crecimiento de E. coli, mientras que un 8.50 ± 0.37% de inhibición con el 3-HPA producido en cultivo MRS con glucosa. Como agente antiséptico de control, se utilizó la clorhexidina al 0.12%, arrojando un 97.61 ± 0.05% de inhibición. Se concluye que la fuente de carbono inicial modifica el potencial antimicrobiano del 3-HPA, siendo la celobiosa un sustrato candidato para continuar su estudio en la optimización de la secreción de metabolitos activos, lo que resalta su importancia en el desarrollo de alternativas para el control microbiano y la economía circular.

Agave and chicory fructans, fractionated into three molecular-weight distributions, exhibit distinct physicochemical and technofunctional properties, highlighting the influence of structural characteristics and molecular size.

El procesamiento de café genera residuos sólidos y líquidos con elevada carga orgánica y potencial contaminante, como la pulpa y las aguas residuales del beneficiado húmedo. La valorización de estos subproductos mediante digestión anaerobia representa una estrategia alineada con la economía circular. Se evaluó la producción de metano a partir de pulpa de café y agua residual del proceso de beneficiado, mediante ensayos en operación batch. Asimismo, se analizaron indicadores de eficiencia y se estimó el potencial energético de ambos sustratos. La pulpa de café alcanzó una remoción de DQO y SV alcanzó 36.23% y 38.7%, respectivamente, con un tiempo de retención hidráulica de 21 días y una producción acumulada de metano de 1.19 L. El agua residual presentó menores remociones (18.4% de DQO y 20% de SV), un TRH de 5.4 días y un volumen de metano de 0.30 L. En términos energéticos, la pulpa mostró mayor potencial para cogeneración eléctrica (31 kJ/L), mientras que el agua residual destacó en la fracción térmica (133 kJ/L), lo que sugiere su aprovechamiento directo en procesos de secado de café.

The growth behavior and lactic acid production capacity including both L-lactic and D-lactic acid isomers of five probiotic strains (Lactobacillus plantarum ATCC® 8014, L. rhamnosus ATCC® 53103, L. casei ATCC® 334, L. reuteri ATCC® 55730, and Bifidobacterium animalis ENCB-IPN) were systematically evaluated using defined carbon sources. Each strain was cultured for 24 h in modified MRS broth, where glucose was replaced with 1% (10 g/L) of individual substrates: monosaccharides (fructose, glycerol, rhamnose, arabinose, mannose, xylose, galactose), disaccharides (sucrose, cellobiose, lactose), a trisaccharide (raffinose), agave-derived fructooligosaccharides (FOS), and high-molecular-weight agave fructans (FAPM, DP > 10). Bacterial growth was monitored via optical density (OD595), and the specific growth rate (μ) and maximum OD were calculated. Fructose supported the highest total lactic acid production, particularly in L. plantarum and B. animalis, followed by sucrose, mannose, and cellobiose. Notably, L. rhamnosus achieved the highest L-lactic acid proportion (96%) with FAPM, while L. casei yielded 92.5% with cellobiose. In contrast, the highest D-lactic acid proportions were obtained with lactose (71.35% in L. plantarum, 55.88% in L. reuteri) and with glycerol in L. casei (62%). Principal component analysis (PCA) showed limited correlation between growth and acid production when monosaccharides were used, but strong positive correlations were found with disaccharides and FOS, particularly between μ and lactic acid yield. This study highlights the relevance of using defined carbon sources to elucidate the substrate-specific metabolic behavior of probiotic strains. The results provide a comparative framework for selecting or engineering strains for targeted lactic acid production (including optical purity) and lay the foundation for future bioprocess optimization using complex substrates such as agro-industrial residues or functional oligosaccharides.

The objective of this work was to evaluate the effect of operating conditions and fructans size distribution on the tight Ultrafiltration process for agave fructans fractionation. A mathematical model of limiting mass flux transfer was used to represent the profile of concentrations over time at the outlet of a pilot scale ultrafiltration system. First, a Box-Behnken experimental design was performed for the optimization of the parameters that determine the operating conditions in their respective ranges: temperature, 30–60 °C; transmembrane pressure (TMP), 1–5 bar and feed concentration, 50–150 kg∙m⁻³, on the separation factor (SF) and permeate flux. Then, the validation of the model for different fructans size distribution was carried out. The results showed that for SF, the quadratic terms of temperature, TMP and feed concentration were the most significant factors. Statistical analysis revealed that the temperature-concentration interaction has a significant effect (p < 0.005) and that the optimal conditions were: 46.81 °C, 3.27 bar and 85.70 kg∙m⁻³. The optimized parameters were used to validate the hydrodynamic model; the adjustments conclude that the model, although simplified, is capable of correctly reproducing the experimental data of agave fructans fractionation by a tight ultrafiltration pilot unit. The fractionation process is favored at higher proportions of FOS:Fc in native agave fructans.

Ceramic and polymeric membrane systems were compared at the pilot scale for separating agave fructans into different molecular weight fractions that help to diversify them into more specific industrial applications. The effect of the transmembrane pressure of ultrafiltration performance was evaluated through hydraulic permeability, permeate flux and rejection coefficients, using the same operating conditions such as temperature, feed concentration and the molecular weight cut-off (MWCO) of membranes. The fouling phenomenon and the global yield of the process were evaluated in concentration mode. A size distribution analysis of agave fructans is presented and grouped by molecular weight in different fractions. Great differences were found between both systems, since rejection coefficients of 68.6% and 100% for fructans with degrees of polymerization (DP) > 10, 36.3% and 99.3% for fructooligosaccharides (FOS) and 21.4% and 34.2% for mono-disaccharides were obtained for ceramic and polymeric membrane systems, respectively. Thus, ceramic membranes are better for use in the fractionation process since they reached a purity of 42.2% of FOS with a yield of 40.1% in the permeate and 78.23% for fructans with DP > 10 and a yield of 70% in the retentate. Polymeric membranes make for an efficient fructan purification process, eliminating only mono-disaccharides, and reaching a 97.7% purity (considering both fructan fractions) with a yield of 64.3% in the retentate.