Immobilization of Psilocybe castanella on ceramic (slate) supports and its potential for soil bioremediation

The objective of the present study was to develop and characterize a support for the immobilization of Psilocybe castanella in order to optimize the process of incorporation of fungal inoculum into the soil. The ceramic supports were fabricated from slate powder in the shape of hollow spheres by the slip casting technique (suspension: 40% v/v). The sintering temperature was evaluated in the range of 850–1,070°C and porosity was analyzed by mercury intrusion. The temperature of 1,050°C was the most adequate for sintering of the ceramic supports, with the porosity obtained being less than 1%. The fungus was immobilized on the ceramic supports containing lignocellulosic substrate using disks of fungal mycelium grown on 2% malt agar as the inoculum. Fungal biomass was estimated by the quantification of ergosterol. Peroxidase and laccase activities were determined by the oxidation of ABTS in the presence and absence of H₂O₂, respectively. The efficiency of the immobilized inoculum was tested in a grinder containing coarse sand for 45 min at 75 rpm. The supports were colonized with P. castanella and enzymatic activities were detected after the fifth day of fungal growth. Immobilization of the fungus on the ceramic support provided 80% protection of the inoculum against loss of efficiency during mixture with soil. The results demonstrate the potential of the ceramic supports produced with slate powder for immobilization of basidiomycetous fungi and for application to soil bioremediation processes.