Bacteria are a common group of foodborne pathogens presenting public health issues with a large economic burden for the food industry. Our work focused on a solution to this problem by evaluating antibiotic activity against two bacteria (Listeria monocytogenes and Escherichia coli) of relevance in the field of foodstuffs. We used two approaches: (i) structural modification of the antimicrobial peptides and (ii) nano-vehiculisation of the modified peptides into polymer-coated liposomes. To achieve this, two antimicrobial peptides, herein named ‘peptide +2′ and ‘peptide +5′ were synthesised using the solid phase method. The physicochemical characterisation of the peptides was carried out using measurements of surface tension and dynamic light scattering. Additionally, nanoliposomes were elaborated by the ethanol injection method and coated with a cationic polymer (Eudragit E-100) through the layer-by-layer process. Liposome characterisation, in terms of size, polydispersity and zeta potential, was undertaken using dynamic light scattering. The results show that the degree of hydrophilic modification in the peptide leads to different characteristics of amphipathicity and subsequently to different physicochemical behaviour. On the other hand, antibacterial activity against both bacteria was slightly altered after modifying peptide sequence. Nonetheless, after the encapsulation of the peptides into polymer-coated nano-liposomes, the antibacterial activity increased approximately 2000-fold against that of L. monocytogenes.

Antimicrobial peptides (AMPs) are effector molecules of the innate immune system and have been isolated from multiple organisms. Their antimicrobial properties are due to the fact that they interact mainly with the anionic membrane of the microorganisms, permeabilizing it and releasing the cytoplasmic content. Alyteserin 1c (+2), an AMP isolated from Alytes obstetricans and its more cationic and hydrophilic analogue (+5) were synthesized using the solid phase method, in order to study the interaction with model membranes by calorimetric and spectroscopic assays. Differential scanning calorimetry (DSC) showed that both peptides had a strong effect when the membrane contained phosphatidylcholine (PC) alone or was mixed with phosphatidylglycerol (PG), increasing membrane fluidization. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to study the secondary structure of the peptide. Peptide +2 exhibited a transition from β-sheet/turns to β-sheet/α-helix structures after binding with model membranes, whereas peptide +5 had a transition from aggregation/unordered to β-sheet/α-helix structures after binding with membrane-contained PC. Interestingly, the latter showed a β-sheet structure predominantly in the presence of PG lipids. Additionally, molecular dynamics (MD) results showed that the carboxy-terminal of the peptide +5 has the ability to insert into the surface of the PC/PG membranes, resulting in the increase of the membrane fluidity.

There is ongoing interest in the alcohol industry to significantly reduce and/or add value to the liquid residue, vinasse, produced after the distillation and rectification of ethanol from sugar cane. Vinasse contains potassium, glycerol, and a protein component that can cause environmental issues if improperly disposed of. Currently, some industries have optimized their processes to reduce waste, and a significant proportion of vinasse is being considered for use as an additive in other industrial processes. In the manufacture of cement and asphalt, vinasse has been used in the mixtures at low concentrations, albeit with some physical and mechanical problems. This work is the first molecular approximation of the components of the sugar cane vinasse in an industrial context, and it provides atomic details of complex molecular events. In the current study, the major components of sugar cane vinasse, alone or complexed on the surface of calcium carbonate, were modeled and simulated using molecular dynamics. The results showed that the protein component, represented by the mannoprotein Mp1p, has a high affinity for forming hydrogen bonds with potassium and glycerol in the vinasse. Additionally, it provides atomic stability to the calcium carbonate surface, preserving the calcite crystalline structure in the same way potassium ions interact with the carbonate group through ion–dipole interactions to improve the cohesion of the modeled surface. On the contrary, when the glycerol molecule interacts with calcium carbonate using more than two hydrogen bonds, it triggers the breakdown of the crystalline structure of calcite expanding the ionic pair.

La vinaza de caña de azúcar, al ser un residuo producido en altas cantidades derivado de los procesos industriales para la producción de Etanol, es una mezcla de compuestos que tiene una utilidad cíclica para matrices de suelos debido a su composición natural e industrial que recaen en las ventajas y desventajas de sus aplicaciones. El potasio y el glicerol, compuestos mayoritarios en su composición, son ligandos que ayudan a la conformación de complejos proteicos con la vinaza para tener alternativas en los usos industriales como aditivos para alimento animal y fertilizantes en matrices de suelos, muchos de estos, utilizados en cultivos de las mismas industrias. Estudios de química computacional permiten conocer propiedades intermoleculares entre la vinaza, el glicerol y el potasio mediante in-Interacciones intermoleculares de la proteína de membrana arf*gtp con potasio y glicerol, componentes mayoritarios de la vinaza de caña de azúcar teracciones moleculares estables convirtiéndola en una herramienta útil de evaluación de dichas propiedades y determinación de nuevas alternativas para usos industriales de este residuo. En esta investigación, se evaluó la dinámica de las interacciones intermoleculares entre el modelo proteínico tridimensional extraído del archivo de la base de datos de proteínas (PDB) por sus siglas en inglés, del modelo (2KSQ), el cual consiste en una proteína de membrana de la Echoli llamado Arf*GTP, con dos ligandos como potasio y glicerol mediante dinámica molecular utilizando un software llamado Dinámica Molecular Escalable por sus siglas en inglés, NAMD1. Se observaron y evaluaron las interacciones intermoleculares por medio del software llamado Visor de Dinámica Molecular por sus siglas en in-glés, VMD2 de la molécula modelada de la proteína de membrana Arf*GTP con componentes mayoritarios, tales como, el potasio y el glicerol en un ambiente solvatado definido e implícito de modelo de caja de agua (TIP3) con el fin de identificar y caracterizar las fuerzas intermoleculares, equilibrio en trayectorias, fluctuaciones atómicas, afinidades, constantes de velocidad e interacciones Arf*GTP-Potasio, Arf*GTP-Glicerol y Arf*GTP-Potasio-Glicerol en el contexto de usos industriales de la vinaza como alimento animal y fertilizantes. Final-mente, se observó que los tres complejos Arf*GTP se ven favorecidos por afinidades posicionales de los ligandos como los aminoácidos GLN 155, para el caso del potasio, y para los gliceroles lo fueron GLY 27 y LYS 127, como también, apantallamientos de algunos átomos de los aminoácidos con los ligandos. Con esta investigación, se busca tener más información acerca de las interacciones intermoleculares y constantes de velocidad, equilibrio de trayectorias y afinidades químicas de la proteína de membrana Arf*GTP con otros ligandos orgánicos e inorgánicos que aporten nuevas alternativas industriales para el uso de la vinaza de caña de azúcar.