In situ fabrication of ZIF-8 decorated tezontle for enzyme immobilization towards biodiesel production

Abstract

Efficient and cost-effective materials for enzyme immobilization have been sought to enhance the stability and recyclability of enzymes. We have developed highly efficient, stable, resistant, and reproducible biocatalysts in this work. The fabricated catalysts (ZIF-8/tezontle/lipase) are economical, stable, and obtained at room temperature. The prepared materials were confirmed through diffraction planes and crystals of ZIF-8 (hexagonal shape) on the surface with a size of ca. 0.715 to 1.42 μm. The characteristic elements of ZIF-8, such as N and Zn, and functional groups in the prepared composites were also analyzed. The thermal stability profiles were conducted to determine the total composition loss of the prepared material compared to pristine ZIF-8. As for the feedstock and DB, it is observed that they have an acidity index of 0.67 mg KOH per g for oil and 0.2 mg KOH per g for DB, complying with the parameters established by ASTM, while the moisture increases for the DB (0.075%) because the BD is hygroscopic. In addition, it exhibited a recyclability efficiency of 91% for the composite material compared to pristine tezontle and ZIF-8 catalysts due to its comparable porosity, surface area, and surface functional groups that allow enzyme–support binding, thereby enabling lipase recyclability. Post-biodiesel analysis confirmed the reduction in chain length during the transesterification process.