Análisis de las interacciones fisicoquímicas y ecológicas en los mecanismos de antagonismo entre hongos ocratoxigénicos presentes en cerezas de café y bacterias ácido lácticas
Coffee is considered a product of great importance in world trade. However, since 1960 the presence of mycotoxins has been detected in various foods, not just coffee. Mycotoxins, such as ochratoxin A (OTA), is associated with various neurotoxic, genotoxic, teratogenic disorders, among other disorder...
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| Tipo de recurso: | tesis de maestría |
| Estado: | Versión publicada |
| Fecha de publicación: | 2019 |
| País: | México |
| Institución: | Universidad Autónoma Metropolitana |
| Repositorio: | Repositorio Institucional de la UAM Iztapalapa |
| Idioma: | español |
| OAI Identifier: | oai:bindani.izt.uam.mx:w6634388s |
| Acceso en línea: | https://doi.org/10.24275/uami.w6634388s |
| Access Level: | acceso abierto |
| Palabra clave: | info:eu-repo/classification/LEM/Aspergillus info:eu-repo/classification/LEM/Café info:eu-repo/classification/LEM/Coffee info:eu-repo/classification/cti/6 |
| Sumario: | Coffee is considered a product of great importance in world trade. However, since 1960 the presence of mycotoxins has been detected in various foods, not just coffee. Mycotoxins, such as ochratoxin A (OTA), is associated with various neurotoxic, genotoxic, teratogenic disorders, among other disorders in animals and humans. In addition, the contaminated grains cause significant economic losses for the agricultural sector (932 million dollars / year). The main microorganisms that produce mycotoxins are fungi of the genus Aspergillus, Penicillium and Fusarium. Objective. With this background, the objective of this work is to determine the physicochemical and ecological interactions involved in the biocontrol of the Aspergillus carbonarius (considered as the largest producer of OTA in food) and the production of ochratoxin A in coffee beans, with the application of lactic acid bacteria "Lactobacillus plantarum" endemic of coffee pulp. Understanding the mode of action of L. plantarum and the influence of physicochemical factors on the bacterium-fungus interaction will generate biotechnological alternatives that allow making recommendations to prevent, control or eliminate ochratoxin A from coffee crops. Methods. For this purpose, using scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), atomic force microscopy (AFM), light field microscopy (LFM), Zeta potential (ZP), Fouriertransform infrared spectroscopy (FTIR), the physicochemical mechanisms in the cell-cell interaction are studied making surface characterizations such as roughness, topography, chemical composition, surface charge and hydrophobicity of both microorganisms, which could be involved in the adhesion between both microorganisms and their association with the biocontrol of A. carbonarius. Results. We determined that L. plantarum inhibits fungal (radial) development in solid medium above 50% for 5-6 days (fungistatic biocontrol). The maximum inhibition (84%) is reached on the fourth day, using bacterial inoculum of 5x104 cell/mL. In the co-cultures in liquid medium we observed the effect of biocontrol on the germination of fungal spores up to 72 h. On the other hand, the production of L-lactic acid, D-lactic acid, formic acid, acetic acid, propionic acid and ethanol was characterized by HPLC, as fermentation products of trehalose by L. plantarum, molecules suggested in literature regarding fungal biocontrol. Interaction studies (co-culture) showed bacterial adhesion on the surface of fungal spores as antagonist mechanism, classified in literature as direct antagonism. In addition to this, possible damage to the surface of fungal spores was determined by the presence of membrane pores of approximately 140 ± 22.3 nm, which could be related to the biocontrol of the mycotoxigenic fungus. In addition to this study, the capacity of OTA adsorption on the surface of L. plantarum was determined. Finally, the mechanisms responsible for superficial adhesion of lactic acid bacteria on fungal spores were analyzed. The PZ of bacteria and fungi (-11 a -18 mV y 0 a -10 mV respectively) they do not support the hypothesis of electrostatic attraction as the mechanism responsible for adhesion (observed in SEM). On the other hand, the roughness and topography theoretically suggest that roughness could be a determining factor in the bacterial adhesion. However the numerical value of superficial roughness of fungal spores estimated under the arithmetic average of the absolute values of the heights Ra = 0.097±0.031 µm, it does not relate to a great extent the roughness with the adhesion observed. On the other hand, by LCSM and FTIR, superficial chemical bonds were determined, which were associated to proteins and polysaccharides as possible membrane biomolecules involved in the adhesion of L.plantarum on spores of A. carbonarius. Finally, the results obtained in this work propose the effective use of L. plantarum as an alternative for the control of A. carbonarius. Likewise, the physical, chemical and ecological mechanisms of biocontrol studied in this work allow us to understand the mode of action of L. plantarum, which broadens possibilities and opportunities to generate new biotechnological alternatives against fungal contaminants of crops and their mycotoxins. |
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