Micropellets of Pleurotus ostreatus for copper removal: Influence of nutritional conditions and laccase activity on adsorption

Pleurotus ostreatus has emerged as a promising model for heavy metal bioremediation. Given the known role of laccases in copper oxidation, it was hypothesized that higher laccase activity would correlate with increased copper removal. This study evaluated how the composition of the culture medium influences copper adsorption and its relationship with copper-induced laccase activity in this fungus. Fungal pellets were produced in two different media, and their morphological characteristics, laccase activity, and copper removal capacity were evaluated. The results show that, contrary to expectations, pellets with more complex morphology and higher laccase activity exhibited a maximum copper loading capacity approximately six-fold lower than those produced in media with lower laccase activity. Analysis of the pellets by SEM-EDX, FTIR, and confocal microscopy revealed some physicochemical differences. Pellets with higher copper loading capacity had higher fluorescence suggesting more cell wall polysaccharide content, but lower laccase activity. These results offer a possible link between copper removal and copper-induced laccase activity associated with compositional medium for fungal culture. This finding represents a novel approach to designing and optimizing fungal biotechnological solutions in heavy metal bioremediation.