Abstract

Various applications of extracellular enzymes from white-rot fungi as biocatalysts have been reported in pulp bleaching, wastewater treatment and soil remediation. However, their use in industrial applications has been limited by several factors, mainly the high enzyme cost, the low operational stability and the low or no recovery options. The enzyme immobilization has demonstrated to be a good technology that may allow their practical application. Fungal enzymes have been successfully immobilized on porous glass beads and on various clay minerals for soil pollutants degradation. Nanomaterials of natural origin, such as nanoclays, have not been proved yet. The aim of this study was to obtain nanoclays as support material for the immobilization of manganese peroxidase (MnP) from the white rot fungus Anthracophyllum discolor. Andisol of the South of Chile, from the Temuco Series, was used for nanoclays obtention. The clay fraction was obtained by a sedimentation method based on Stokes's law, without destruction of the organic matter. 5 g clay was suspended in 100 mL NaCl 1 M, with agitation for 48 h. The suspension was centrifuged at 3,000 rpm for 40 min and the supernatant was discarded. Clay was re-suspended in 50 mL of filtered and deionized water, under moderate agitation for approximately 1 h, and then centrifuged under the same previous conditions. The procedure was repeated 7 times. The recovered supernatants were dialyzed until a conductivity range between 0.5 to 0.8 µS, and than concentrated. For its characterization, nanoclays were analyzed by transmission electronic microscopy and its isoelectric point was determined by microelectrophoresis. Electrophoretic mobilities were measured with a zeta meter (ZM-77) apparatus. Dilute dispersions (0.05 g/liter) were prepared in 10-3 M KC1. The pH was adjusted with 10-2 M HC1 or NaOH. The mobilities were averaged and the zeta potential calculated using the Helmholtz-Smoluchowski equation. The results indicate that the obtained material corresponds to nanoclays with a particle average size less than 100 nm, without the presence of electronic diffraction and with an isoelectric point (pi = 3.2 ) closed to that of clay. Future studies will be focused on the evaluation of the immobilization efficiency of MnP from A. discolor in this new natural nanomateria