Immobilization of commercial laccase on spent grain

Abstract

The aim of this work was to assess the possibility of using beer spent grain (a byproduct of beer’s brewing industry) as a carrier for laccase immobilization. Both adsorption (on spent grain – SG and on digested spent grain – DSG) and covalent binding (using glycidol and glycidol followed by ethylenediamine on DSG) were used. The effect of different immobilization conditions on the immobilization yields and recovered activities such as contact time, enzyme concentration and pH was evaluated. For the best conditions, immobilization yields, recovered activities and thermal, operational and storage stabilities were also evaluated. Finally, the Michaelis–Menten mechanism was applied and the parameter with respect to ABTS oxidation was determined. Enzyme immobilization on DSG led to the best enzyme activities (recovered activities as high as 90%) and to high storage and operational stabilities (10 cycles). Thermal stability was also improved and the half-life of immobilized laccase in SG increased from 0.64 h to 1.1 h at 70 ◦C