Aminated lignin mesoporous carbon as advanced support for high-performance lipase immobilization

In this study, alkali lignin (AL), a low-cost and renewable biopolymer, was innovatively selected as the precursor. Modified lignin, namely aminated lignin (AAL), sulfomethylated lignin (SML) and phosphorylated lignin (PAL), were synthesized and combined with nano-MgO to serve as a template. Subsequent carbonization of these mixtures produced mesoporous carbon (MC) carriers denoted as AL-MC, AAL-MC, SML-MC and PAL-MC. Rhizomucor miehei lipase (RML) immobilization onto these carriers was effectively achieved through physical adsorption under mild conditions. Through optimization of the preparation parameters, high-performance immobilized enzymes (IM-AL-MC, IM-AAL-MC, IM-SML-MC, IM-PAL-MC) were developed. Notably, IM-AAL-MC exhibited superior enzyme activity (0.037 U/mg immobilized lipase), loading capacity (0.145 mg protein/mg immobilized lipase) and immobilization efficiency (84.5 %). The catalytic efficiency and stability of IM-AAL-MC were comprehensively examined. Characterization of the carriers and immobilized enzymes was conducted using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller surface area analysis (BET) and transmission electron microscopy (TEM). Results indicated that IM-AAL-MC displayed significantly improved stability compared to free lipase. Remarkably, IM-AAL-MC retained 99.49 % activity in n-hexane, far exceeding the free lipase (43.53 %). Additionally, IM-AAL-MC preserved 86.2 % of its relative activity after six consecutive reuse cycles.