Biocatalysts Based on Lipases Immobilized in Multifunctional Inorganic Matrices for the Sustainable Generation of Biodiesel from Wet Microalgae Biomass

Abstract

Biodiesel, consisting of a mixture of alkyl esters of fatty acids, is an important source of renewable energy. Despite scientific advancements in the field, there is a need to overcome some technological obstacles to increase the productive efficiency of Brazilian biofuels. In the context of economically viable exploration of new raw material sources, the oil present in wet microalgae biomass is one of the most promising substrates for biodiesel production, as it substitutes the use of food oils; and microalgae can be rapidly produced on a large scale, simultaneously sequestering a high amount of CO2. Regarding catalytic processes, it is crucial to overcome the limitations of traditional homogeneous catalysts, such as saponification (basic catalysts), slow reaction rates (acidic catalysts), and extraction, separation, and purification steps that increase process costs. A promising alternative involves the use of heterogeneous biocatalysts obtained from enzyme immobilization on inorganic matrices. Currently, lower-cost enzymes are commercially available and, when immobilized, can have increased stability (thermal, pH variation, etc.) and enzymatic activity, as well as being easily recovered and/or reused in different reaction systems. In this context, the present project aims to synthesize and characterize new biocatalysts based on fungal lipases (Thermomyces lanuginosus) immobilized on multifunctional inorganic matrices. The novelty of this proposal lies in the use of innovative supports for enzyme immobilization. Two classes of inorganic solids will be investigated: (i) hierarchical zeolites with mixed crystallographic structures containing transition metals with octahedral and pentahedral coordinations; and (ii) nanocomposites based on carbonaceous material/mixed metal oxides derived from layered double hydroxides. Such new heterogeneous biocatalysts are strong candidates for biodiesel production, as they have potential synergistic effects combining the enzymatic catalysis of fungal lipases with the chemical catalysis of inorganic matrices (acid-base properties). The application of these catalysts will be explored in the hydroesterification and transesterification reactions of lipids extracted from wet microalgae biomass to obtain biodiesel in a more sustainable manner. Thus, this project is strategic for Brazil, as it will contribute to the industrial implementation of new catalytic processes, ensuring the country's energy security and reducing greenhouse gas emissions. (AU)