Immobilization of fungal laccase on peanut shell carriers

Abstract

Supported enzymes are more stable than free enzymes, can be reused and easily separated from reaction products, which makes them even more interesting. On the other hand, research into alternatives for the use of residual biomass in the context of the circular economy is crucial. The aim of this work was to investigate the use of peanut shells (PS) and its derivative biochar (PSB) as carriers for the immobilization of Phlebia brevispora BAFC 633 fungal laccase (Lac). No significant differences were found between the enzymatic activity of Lac immobilized on PS or PSB using 2,6-dimethoxyphenol as substrate, so only PS was used for further studies. A screening design was performed with the following immobilization parameters: Contact time, Lac concentration, PS concentration and agitation. The analysis of variance showed that the factors with a statistically significant influence on the promoted enzyme activity (U g^-1) were the agitation and the Lac concentration. For optimization, both factors were further investigated, improving the Lac activity on PS to 0.170 ± 0.042 U g⁻¹, which corresponds to a 2.3-fold relative increase in activity yield. The immobilization efficiency was high, but a decrease in activity was observed with increasing enzyme loading. The evaluation of the results using adsorption equilibria and the estimation of the fractional occupancy of the Lac indicate a still low surface occupancy. Considering its low cost, easy preparation and acceptable activity, PS/Lac biocatalysts are promising alternatives for water remediation.