Abstract: The objective of this investigation was the optimization of the immobilization of naringinase from Penicillium decumbens by entrapment in poly(vinyl alcohol) and polyethylene glycol cryogels. First, the effect of the characteristics of the matrix components on immobilization efficiency and mechanical stability of the biocatalyst obtained, was determined. Experimental design and response surface methodology was used to analyse the effect of pH (3.0-8.0), the concentrations of poly(vinyl alcohol) (5.3-8.7%) and polyethylene glycol (7.0-12.0%) on the immobilization efficiency, and to optimize these parameters. Additionally, reuse capacity in synthetic juices of immobilized enzyme was studied. The immobilized biocatalysts obtained, conserved 45-47% of active enzyme, and, after three cycles of reuse in synthetic juice, retained 54.3% of their initial activity. Results showed that immobilization efficiency and operational stability of entrapped naringinase were affected by immobilization conditions.

Resumen: El objetivo de esta investigación fue optimizar la inmovilización de naringinasa de Penicillium decumbens mediante atrapamiento en criogeles de alcohol polivinílico y polietilenglicol. En primer lugar, se determinó el efecto de las características de los componentes de la matriz sobre la eficacia de inmovilización y la estabilidad mecánica de los biocatalizadores obtenidos. Se empleó la herramienta de diseño de experimentos y superficie de respuesta para analizar el efecto del pH (3,0-8,0), de las concentraciones de alcohol polivinílico (5,3-8,7%) y polietilenglicol (7,0-12,0%) sobre la eficacia de inmovilización, y para optimizar estos parámetros. Adicionalmente, se estudió la capacidad de reutilización de los inmovilizados en zumos sintéticos. Se consiguieron biocatalizadores inmovilizados que conservaban un 45-47% de la enzima activa y que, tras tres ciclos de reutilización en zumo sintético, mantenían un 54,3% de la actividad inicial. Los resultados obtenidos mostraron que las condiciones de inmovilización afectaban a la eficacia de inmovilización y a la estabilidad operativa de la naringinasa atrapada.

ABSTRACT: In this work, barley seed coating with urease and phosphatase, free and immobilized in humic acids, was studied as a tool to enhance the use efficiency of N and P by plants. The seeds were encapsulated in gels of Ca-alginate by a method that allows gelation of the polymer, containing enzymes, from the surface of seeds outward. The coating process did not affect seed germination. A pot experiment with the coated seeds was carried out. The seed coating with free enzymes increased soil ammonium-N (NH4+-N) and inorganic P up to 39 and 54 %, respectively, and up to 62 and 64 %, with the immobilized enzymes, in comparison with control pots. Seed coating improved N (47-137 %) and P (29-61 %) uptake by plants. Moreover, a synergistic response in N and P uptake with both urease and phosphatase was observed. It can be concluded that the seed coating with urease and phosphatase exerted a positive effect enhancing the use of N and P by plants, which could lead to the development of natural fertilizers, minimizing the application of chemical fertilizers.