Laccase immobilization and insolubilization: from fundamentals to applications for the elimination of emerging contaminants in wastewater treatment

Abstract

Over the last few decades many attempts have been made to use biocatalysts for the biotransformation of emerging contaminants in environmental matrices. Laccase, a multicopper oxidoreductase enzyme, has shown great potential in oxidizing a large number of phenolic and non-phenolic emerging contaminants. However, laccases and more broadly enzymes in their free form are biocatalysts whose applications in solution have many drawbacks rendering them currently unsuitable for large scale use. To circumvent these limitations, the enzyme can be immobilized onto carriers or entrapped within capsules; these two immobilization techniques have the disadvantage of generating a large mass of non-catalytic product. Insolubilization of the free enzymes as cross-linked enzymes (CLEAs) is found to yield a greater volume ratio of biocatalyst while improving the characteristics of the biocatalyst. Ultimately, novel techniques of enzymes insolubilization and stabilization are feasible with the combination of cross-linked enzyme aggregates (combi-CLEAs) and enzyme polymer engineered structures (EPESs) for the elimination of emerging micropollutants in wastewater. In this review, fundamental features of laccases are provided in order to elucidate their catalytic mechanism, followed by different chemical aspects of the immobilization and insolubilization techniques applicable to laccases. Finally, kinetic and reactor design effects for enzymes in relation with the potential applications of laccases as combi-CLEAs and EPESs for the biotransformation of micropollutants in wastewater treatment are discussed.

A Short Review of Techniques for Phenol Removal from Wastewater

“…They each then carry out successive oneelectron oxidation of reducing substrates like phenols to form the corresponding phenoxy radicals, and these radicals couple non-enzymatically to form dimers. Additional enzymatic cycles with these dimers lead eventually to polymers [70].…”

“…SBP has proven to be an effective enzyme to remove phenol [70,71]. Immobilization techniques such as support-or carrierbinding through physico-chemical interaction, encapsulation which traps enzyme inside the pores of the support, or covalent cross-linking of enzyme functional groups have been investigated to enable large-scale enzymatic treatment [70].…”

Laccase Immobilization on Poly(p-Phenylenediamine)/Fe3O4 Nanocomposite for Reactive Blue 19 Dye Removal

“…More importantly, the development of various nanostructure carriers for enzyme immobilization facilitates a broader range of applications and an increased efficiency for enzyme attachment [10,11]. More importantly, the development of various nanostructure carriers for enzyme immobilization facilitates a broader range of applications and an increased efficiency of immobilized enzymes [12][13][14]. Furthermore, for some redoxases that require an electron shuttle for their catalytic reaction, their activity can be enhanced when these enzymes are immobilized on electron-conducting carriers.…”

Study of Biological Treatment of Paper-Pulp Effluent

“…Laccases enzyme activity has been initiated by molecular oxygen (4-electron) whereas, activity of heme-protein peroxidises (HRR) has been initiated by hydrogen peroxide (2-electron). They each carry out one electron oxidation of phenols to form phenoxy radicals which further couple non-enzymatically to form dimers [28].…”

“…Soyabean peroxidase has been found to be more effective than HRP enzyme for the removal of phenol [28,29]. Rezvani et al [30] studied immobilized SBP for the removal of phenol in a semi-permeable alginate membrane with 97 % removal efficiency at 56 °C.…”