Contribution to the study of the enzymatic degradation of organic micropollutans in waste water

Abstract

Consulta en la Biblioteca ETSI Industriales (Riunet)

[EN] Industrial discharges, urban wastes, consumer products or cleaning agents are some of the sources of organic micropollutants in water. Their concentration, of the order of pg/l up to μg/l, is enough to classify them as persistent, bio-accumulative and toxic substances. They are not efficiently removed by existing techniques. Laccases have been reported to efficiently oxidize organic micropollutants by a green process. In order to consider them an economically feasible application, they are frequently immobilized on a solid carrier. In this study, a covalent immobilization of laccase from Coriolopsis gallica on silica beads is performed. However, spectrophotometric standard activity tests to evaluate the activity of enzymes are not reproducible when dealing with immobilized enzymes. Two a priori solutions to this problem are proposed: the addition of a filtration of the immobilized enzymes before the spectrophotometric measurement and a quantification of the possible adsorption of the substrate on the carrier. The filtration led to reproducible results and the adsorption is negligible. However, the modified activity test is not able to quantify mass transfer phenomena. When this test is evaluated in another type of biocatalyst results to be non-reproducible leading to think that different activity tests have to be defined for different biocatalysts. As an alternative technique, isothermal titration calorimetry is applied to measure the activity of immobilized enzymes with different experimental difficulties but showing that it is also valid for this purpose with further work. Key words: laccase, biocatalyst, activity test, mass transfer, adsorption