Sustainable liquid supports for laccase immobilization and reuse: degradation of dyes in aqueous biphasic systems

Abstract

Although there has been a growing interest in the development of sustainable biocatalytic processes, biocatalysts are not the first choice in most applications because they are significantly expensive to be used in homogeneous catalysis and their immobilization onto solid supports brings additional costs and mass transfer limitations. To overcome these shortcomings, aqueous biphasic systems (ABS) constituted by cholinium-based ionic liquids (ILs) and polymers are here proposed, for the first time, as liquid supports for enzymes immobilization and reuse in biocatalysis. The concept of “liquid support” allows to overcome the major drawbacks of using enzymes in homogeneous reactions, and supported enzymes in heterogeneous reaction. The biocatalytic reaction here performed, using laccase for dyes decolorization, takes place in a biphasic/heterogeneous medium, with the enzyme “supported” in the liquid IL-rich phase and the dye and degradation products enriched in the polymer-rich phase. The systems studied allow an easy immobilization, recovery and reuse of the biocatalyst for at least four reaction cycles, with no significant losses in the dye decolorization yield. Compared to solid supports for enzymes immobilization, higher enzymatic activities and reaction yields are obtained with ABS as liquid supports, while also overcoming the safety and environmental concerns of conventional organic solvents used in liquid-liquid heterogeneous reactions, thus representing more sustainable biocatalytic processes.