Aplicación de ciclodextrinas en distintos sectores industriales: Biotecnología enzimática, industria alimentaria y descontaminación de aguas

Las ciclodextrinas (CDs) son oligosacáridos cíclicos naturales que se obtienen a partir de la degradación enzimática de uno de los polisacáridos más importantes de la naturaleza, el almidón. Las CDs pertenecen a una familia de compuestos con estructura tronco-cónica, en cuyo interior existe una cavidad estable de naturaleza hidrofóbica que puede atrapar o encapsular otras moléculas. Esta propiedad que tienen las CDs da lugar a la formación de una interacción de tipo hospedador-huésped, que modifica y/o mejora las características físicas, químicas y/o biológicas de la molécula encapsulada. Las aplicaciones de las CDs son muy diversas, se utilizan principalmente en la industria farmacéutica, industria alimentaria, industria química, cromatografía, catálisis, biotecnología, agricultura, cosmética e higiene, medicina, industria textil y medioambiente. Las CDs se han empleado en tres sectores industriales diferentes con los siguientes objetivos: • En biotecnología enzimática: estudiar el efecto de la presencia de CDs en la actividad enzimática de peroxidasa (POD) ligada y soluble de lombarda y col blanca. • En industria alimentaria: estudiar el efecto de la presencia de CDs en la estabilidad del aroma de fresa microencapsulado utilizando diferentes agentes encapsulantes y técnicas de encapsulación. • En descontaminación de aguas residuales: estudiar la aplicación de polímeros de CDs en la eliminación del colorante Rubí Directo de aguas contaminadas tras el teñido de textiles. Queda demostrado en POD de lombarda y col blanca, que las CDs no actúan directamente sobre los grupos funcionales de los aminoácidos de estas enzimas, que son las responsables del pardeamiento de frutas y hortalizas. La acción inhibidora que muestran las CDs obre esta actividad enzimática se debe al atrapamiento del sustrato en la cavidad interna de las CDs, retirándolo así del medio de reacción. El estudio de esta inhibición sirve como método para calcular la constante de complejación entre un sustrato concreto y un tipo de CDs. La presencia de CDs como complemento en la mezcla de agentes encapsulantes de aroma de fresa, tiene un efecto protector sobre los componentes volátiles del aroma durante el almacenamiento a diferentes temperaturas. Este efecto protector es dependiente del compuesto analizado y de la técnica de secado utilizada en el proceso de encapsulación, siendo la técnica de lecho fluido la que más lo evidencia. En el caso del aroma de fresa, el compuesto mejor protegido por las CDs es alcohol bencílico. Los polímeros de CDs y EPI pueden utilizarse con éxito en la eliminación del colorante Rubí Directo de aguas residuales de tintado de textiles. Los estudios cinéticos demuestran que el proceso de absorción de Rubí Directo por los distintos polímeros de CDs estudiados, es rápido y uniforme y en él están implicados la quimisorción y la difusión intrapartícula. Este es un proceso complejo en el que intervienen, además de la presencia de CDs para formar complejos de inclusión, interacciones de intercambio iónico por la presencia de grupos carboxilo.Ciencias AmbientalesCiencias de la Alimentació

Pulsed light inactivation of mushroom polyphenol oxidase: a fluorometric and spectrophotometric study

Polyphenol oxidase (PPO) is one of the most important food enzymes, it is responsible for the browning of many foods. Pulsed light (PL) is a non-thermal method of food preservation that is able to inactivate PPO. The aim of this work was to gain insight into the mechanism of PPO inactivation by PL. To this, the kinetics of PPO inactivation by PL was measured, together with associated changes in tryptophan fluorescence, KI fluorescence quenching and turbidity; and results were analysed by parameter A and phase diagram methods. Enzyme inactivation followed the Weibull model. Tryptophan fluorescence decreased during PL treatment, as well as the parameter A, while Stern-Volmer constants increased and turbidity was constant. The phase diagram showed only two populated states. There was a high correlation between the loss of activity and parameter A. Results indicate that under the experimental conditions, the inactivation of PPO by PL is an all-or-none process where the enzyme progressively unfolds with no evidence of aggregation.Fundación Universitaria San Antonio de CartagenaCiencias de la Alimentació

Pulsed light inactivation of horseradish peroxidase and associated structural changes

Pulsed light (PL) is a non-thermal preservation method in which foods are subjected to one or several intense pulses of wide-spectrum light. Peroxidase (POD) is an enzyme that needs to be inactivated or inhibited because of its deleterious effects on the quality of fruits and vegetables. The feasibility of using PL to inactivate POD was tested and results explained based on measurements of UV–vis spectrum, farUV circular dichroism and tryptophan fluorescence, and the phase-diagram method. PL reduced the activity of POD by more than 95% after applying 128 J cm 2 . There was observed a decrease in the Reinheitzahl value and ellipticity and an increase in tryptophan fluorescence at incremental fluences, as well as linear phase diagrams. The study indicates that the inactivation of POD by PL is an all-or-none process related to loss of helical structure, weak unfolding and ejection of the prostetic group.Ciencias de la Alimentació

Adsorption of Direct Blue 78 using chitosan and cyclodextrins as adsorbents

The dyeing industry is one of the most polluting in the world. The adsorption of dyes by polymeric matrixes can be used to minimize the discharge of dyes into the environment. In the present study, chitosan-NaOH and β-cyclodextrin-epichlorohydrin polymers were used to remove the dye Direct Blue 78 from a wastewater model. To understand the adsorption behavior of Direct Blue 78 onto the polymers, adsorption rate and maximum adsorption capacity were calculated using kinetic tests and isotherm curves respectively. The kinetic data and mechanism of the adsorption process were analyzed by three models and the equilibrium data by three adsorption isotherms; also the different thermodynamic parameters were calculated. Results showed that the adsorption process follows pseudo-second-order kinetics in both polymers and the Langmuir isotherm best-fitted data for chitosan-NaOH polymer and the Freundlich isotherm for the β-CDs-EPI polymer. The adsorption process is exothermic in both cases and spontaneous for the β-CDs-EPI polymer to a certain temperature and not spontaneous for the chitosan-NaOH polymer and β-CDs-EPI polymer at higher temperatures. The complementary action of an advanced oxidation process eliminated >99% of the dye from water. The coupled process seems to be suitable for reducing the environmental impact of the dyeing industry.Ciencias de la Alimentació

Adsorption Properties of β- and Hydroxypropyl-β-Cyclodextrins Cross-Linked with Epichlorohydrin in Aqueous Solution. A Sustainable Recycling Strategy in Textile Dyeing Process

β-cyclodextrin (β-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD) were used to prepare insoluble polymers using epichlorohydrin as a cross-linking agent and the azo dye Direct Red 83:1 was used as target adsorbate. The preliminary study related to adsorbent dosage, pH, agitation or dye concentration allowed us to select the best conditions to carry out the rest of experiments. The kinetics was evaluated by Elovich, pseudo first order, pseudo second order, and intra-particle diffusion models. The results indicated that the pseudo second order model presented the best fit to the experimental data, indicating that chemisorption is controlling the process. The results were also evaluated by Freundlich, Langmuir and Temkin isotherms. According to the determination coefficient (R2), Freunlich gave the best results, which indicates that the adsorption process is happening on heterogeneous surfaces. One interesting parameter obtained from Langmuir isotherm is qmax (maximum adsorption capacity). This value was six times higher when a β-CDs-EPI polymer was employed. The cross-linked polymers were fully characterized by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA). Also, morphology and particle size distribution were both assessed. Under optimized conditions, the β-CDs-EPI polymer seems to be a useful device for removing Direct Red 83:1 (close 90%), from aqueous solutions and industrial effluents. Complementarily, non-adsorbed dye was photolyzed by a pulsed light driven advanced oxidation process. The proposed methodology is environmental and economically advantageous, considering the point of view of a sustainable recycling economy in the textile dyeing process.Ciencias Ambientale