Aplicação de lacases na degradação de corantes sintéticos

Abstract

Laccases are enzymes belonging to the class of oxirredutases, which do not require hydrogen peroxide as a co-substrate. It can be found in a wide variety of organisms, such as bacteria, insects, plants, fungus. Where the white rot fungus is the most responsible for its production. These enzymes have a wide variety of substrates and then, have a wide range of technological applications ranging from pulping of cellulose pulp, bleaching of textile fibers and wastewater treatment to food use and organic synthesis. Dyes are one of these substrates of great interest because they are substances that can be recalcitrant, toxic, mutagenic and carcinogenic. These substances are generally difficult to degrade, being stable to the action of light, temperature and chemicals. However, laccases are capable to degrade some dyes because they oxidize phenolic groups contained in their structure. Although, in many cases, it is necessary the presence of mediators to indirectly help the enzyme in the substrate degradation process by transferring the electrons to the oxidation enzymatic reaction, increasing the number of compounds where the enzyme acts. Thus, the objective of this paper was to produce laccases by liquid culture using the Trametes sp., that was efficient in culture medium Agar Extract of Malt and in liquid culture containing residues ligninocelulosicos the application of these enzymes in degradation processes of the Reactive Navy Marine and Violet Crystal, which are synthetic dyes, and evaluate the influence of the chemical redox mediator HBT in its degradation. The activities of the enzymes were determined spectrophotometrically at the wavelength of 420 nm for the laccase, 310 nm for the lignin peroxidase and at 270 nm for the activity of manganese peroxidase. The dye degradation process was determined in a spectrophotometer, with a scan in the region between 400 and 800 nm, and the Reactive Navy Marine dye showed the highest absorption wavelength at 610 nm and the Violet Crystal dye at 584,5 nm and the biodegradation experiments were performed for each dye at its highest wavelength. The degradation of the dyes by the extract in the presence of the mediator was efficient. For comparison purposes, a commercial laccase from Pleurotus ostreatus fungus was used in parallel, and the degradation results were similar to those obtained by the application of Trametes sp. crude extract, both of which reached values above 70% of removal in all experiments , proving the main action of fungal laccases in the process of biodegradation and assuming that the laccase produced in vitro can be used in the degradation of dyes.