Exploring the structural and catalytic features of lipase enzymes immobilized on g-C₃N₄: A novel platform for biocatalytic and photocatalytic reactions

The exploration of multifunctional supporting materials for modern enzyme immobilization is an attractive subject for advanced catalytic applications. In the present study, lipase enzyme types, namely palatase 20,000 L, lipozyme TL100L, and lipozyme CALB, were immobilized on graphitic carbon nitride (g-C₃N₄) using physical and covalent immobilization methods in order to obtain biohybrids for utilization in biocatalytic and photocatalytic reactions. Characterization tests confirmed successful immobilization of enzymes without changing the crystal phase of g-C₃N₄. The immobilization yields were calculated as 71.0% and 93.4% for C₃N₄@PLTS; 81.3% and 95.4% for C₃N₄@LPZYM; and 79.4% and 91.7% for C₃N₄@CALB biohybrids using physical adsorption and covalent bonding methods, respectively. The kinetic constant values of K_m and V_max were significantly higher for immobilized lipases than for free forms. The photocatalytic efficiencies of biohybrid catalysts were also greater than raw g-C₃N₄. Among the lipase types, lipozyme TL100L attached on g-C₃N₄ exhibited the best catalytic performance in both biocatalytic and photocatalytic experiments, which was attributed to its open lid structure. As a result, this study opens the door to utilizing g-C₃N₄ as a support material for the immobilization of different enzymes and establishing catalyzed reactions.