Síntese de corantes naturais pela oxidação de compostos fenólicos utilizando lacases fúngicas

Abstract

Laccases are oxidoreductase enzymes found in different organisms with an important role in their metabolic processes. Due to the ability of these enzymes to modify the structure of phenolic compounds producing natural products with low toxicity, they can be used in biotechnological processes for industrial and environmental applications. The production and use of synthetic dyes has increased in the past years consequently causing more environmental impacts, such as contamination of water due to the release of industrial effluents with a high degree of toxicity. The oxidation process mediated by the laccase, allows the synthesis of natural dyes that can be used in textile, food and cosmetics industries, resulting in less damage to the environment. The aim of the present study was to evaluate the biotechnological potential of fungal laccases for the synthesis of natural dyes. Laccases were produced by individual and co-culture of the fungi Microsphaeropsis arundinis and Trametes villosa in static liquid culture medium containing different inducers of ligninolytic enzymes. After the growth of fungi, the activity of the laccase in the crude enzyme extract was determined spectrophotometrically by monitoring the oxidation of 2,2’-azino-bis (3- ethylbenzothiazoline-6-sulfonic) (ABTS). The enzymatic characterization of the laccase enzyme was analyzed on sodium polyacrylamide-dodecyl sulfate gel (SDSPAGE), with silver staining and ABTS gel zymogram. The synthesis of dyes by the action of laccases was evaluated in reactions with gallic acid, ferulic acid and yerba mate extract. The antioxidant potential of the reaction products was determined using the methods of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and Ferric Reducing Antioxidant Power (FRAP). It was observed that the co-cultivation of the fungi M. arundinis and T. villosa presented enzymatic activity 99.93% and 26% higher than the individual cultures of M. arundinis and T. villosa, respectively. Three different laccase isoenzymes were identified, two isoenzymes in M. arundinis and one isoenzyme in T. villosa. The natural dyes synthesized in reactions with the laccases presented brown and yellow tones, which varied according to the concentrations of the substrates used in the reaction. The highest antioxidant activity was identified in sample six, obtained by the FRAP method, with 939 μmol/L equivalent of Trolox. The dyes resulting from the reactions between gallic acid and yerba mate extract (10 mg/mL) showed antimicrobial potential, through bacterial agglomeration, against S. aureus. The dyes used for more detailed characterizations showed intense brown colorings, demonstrating a great potential to be used in the cosmetic and textile industries.