Production of electrogenic pigments from new fungal sources applied as electron shuttles in biofuel cells

摘要

This study is based on the isolation and characterization of new biomolecules with electrogenic features that can be used as potential electronic mediators for bioelectrodes in Biological Fuel Cells (BFC). Indigenous filamentous fungi isolated form the Caatinga regions at northeast Brazil were selected as target. The preliminary visual examinations from plates cultivated at 28 °C and 72 h in Sabouraud (SA) agar. Selection was performed in four different media supplemented or not with glycerol. Parameters of intensity of color and excretion to the media, led us to pre-select 12 strains. Finally, only 4 strains which showed the highest production when modified nutrient medium (MNM) was used: Penicillium sp SIS-21, Penicillium sp CP1, Aspergillus sp SIS-4 and Talaromyces sp A2P1. Submerged cultivation were performed during 240 h at 28 °C and 180 rpm, using liquid MNM. The free cell supernatants obtained after filtration and centrifugation were lyophilized and evaluated in terms of pigment concentration by UV-Vis spectrophotometry. Crude extracts were obtained, column chromatography using Ethyl acetate: Ethanol (60:40) as eluent. Pooled and dried samples were extracted by liquid-liquid extraction in (H~+|OH~-) chloroform and the semi-purified pigments were used for organic and bioelectrochemical analyses. Cyclic voltammetry analysis was performed using as working electrode: glassy carbon; counter-electrode: Pt and as reference electrode: Ag|AgCl (in satd KCl), As support electrolytes of H_3PO_4 or KCl both at 100 mmol/l. The performances in terms of mediated electron transportation were studied separately against a bioanode of Glucose Oxidase from Aspergillus niger (GOx) or a biocatode of Laccase from Trametes versicolor (LacTv). These system were compared with the known electron shuttles: bromocresol green, hydroquinone and ABTS. All the evaluated pigments showed good electrochemical features in terms of redox behavior and current output similar to those observed with the standard mediators with both enzymatic systems.