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 Km and Vmax 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.