Effect of Different TiO₂ Morphologies on the Activity of Immobilized Lipase for Biodiesel Production

Abstract

Lipase catalytic activity is greatly influenced by immobilization on nanoparticles. In this study, lipase from Aspergillus niger was immobilized on TiO 2 nanoparticles with different morphologies: microspheres, nanotubes, and nanosheets. All TiO 2 samples were prepared by a hydrothermal method. Lipase/TiO 2 nanocomposites were prepared by a physical adsorption method through hydrophobic interactions. The prepared composites were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). The catalytic activity of free and immobilized lipases was tested using sunflower oil in the presence of methanol to produce biodiesel at 40 °C for 90 min. The lipase immobilized on TiO 2 microspheres showed the highest activity compared to the lipase immobilized on TiO 2 nanotubes and nanosheets. To optimize the lipase-to-microsphere ratio, lipase was immobilized on TiO 2 microspheres in different microspheres/lipase, w/w, (S/L) ratios of 1:1, 1:0.75, 1:0.5, and 1:0.25. It was noticed that the hydrolytic activity follows the order 1:0.25 > 1:0.5 > 1:75 > 1:1. The immobilization yield activities were found to be 113, 123, 125, and 130% for the microspheres/lipase (S/L) ratios of 1:1, 1:0.75, 1:0.5, and 1:0.25, respectively.

A Multicomponent Mannich Reaction Catalyzed by Hydrolases Immobilized on Titanate Nanotubes

“…As previously mentioned, trypsin and α‐chymotrypsin exhibit different specificities [36–39] . However, during the immobilization process, the specificity, catalytic activity, and selectivity of the enzyme can be altered due to structural modifications caused by the interactions between the support and the surface of the enzyme, depending on the enzyme‐support‐substrate ratio [33,39,53–55] …”

“…[36][37][38][39] However, during the immobilization process, the specificity, catalytic activity, and selectivity of the enzyme can be altered due to structural modifications caused by the interactions between the support and the surface of the enzyme, depending on the enzyme-support-substrate ratio. [33,39,[53][54][55] Using NtsTi, a significant result was observed, with the antiisomer obtained at a conversion of 69 % and a diastereomeric ratio of 21 : 79 syn : anti. Titanate nanotubes are ionic hydrophilic compounds with high specific surface areas, reaching up to 227.767 m 2 g À 1 .…”

“…[24,[26][27][28][29][30] In this area, nanostructured titanium dioxide (TiO 2 ) materials have excelled due to their wide applications, [31,32] low-cost preparation, regular and controllable nanoscale geometry, high specific surface area and attractive biocompatibility. [9,[31][32][33] Furthermore, the functional hydroxyl groups present on the surface of titanate nanotubes (NtsTi) can provide an aqueous microenvironment and stabilize the enzyme structure when used in organic solvents. Besides, these materials can be used as catalysts (Brönsted and Lewis acid sites) or co-catalysts.…”

“…Nanostructured materials offer unique and fascinating characteristics that balance key factors determining biocatalyst efficiency, including high surface area, which minimizes mass transfer resistance [24,26–30] . In this area, nanostructured titanium dioxide (TiO 2 ) materials have excelled due to their wide applications, [31,32] low‐cost preparation, regular and controllable nanoscale geometry, high specific surface area and attractive biocompatibility [9,31–33] . Furthermore, the functional hydroxyl groups present on the surface of titanate nanotubes (NtsTi) can provide an aqueous microenvironment and stabilize the enzyme structure when used in organic solvents.…”

Titanate Nanotubes-Based Heterogeneous Catalyst for Efficient Production of Biomass Derived Chemicals

“…A synergetic effect between Na 2 CO 3 and sodium titanate nanotubes was proposed for the increase in the amount of strong basic sites, resulting in an excellent catalytic performance in transformation of triglycerides to methyl esters (97% yield). Interestingly, in other important studies, lipase immobilized onto the sodium titanate nanotubes have recently been employed in the fatty acid methyl esters production ( Nady et al, 2020 ; El-Kady et al, 2021 ). The immobilized lipase gave a high fatty acid methyl esters yield of 83.5% at short time of 90 min and showed the enhanced recycling stability for ten consecutive cycles.…”