Banca de QUALIFICAÇÃO: ISABELA OLIVEIRA COSTA

PRODUCTION OF MULTIENZYME IMMOBILIZED LIPASE SYSTEMS IN COCONUT FIBER FOR THE SYNTHESIS OF BIODIESEL VIA TRANSESTERIFICATION

Biodiesel, Lipases, Immobilization, Green coconut fiber, Residual oil.

Biodiesel production through lipase-catalyzed transesterification is an alternative to traditional chemical catalysts. This clean technology offers greater conversion efficiency, eliminates side reactions and operates at lower temperatures. Enzyme immobilization is applied to improve enzyme stability, facilitating its recovery and reuse and promoting protection against inhibitory effects. The immobilization support can be from various sources, including lignocellulosic waste, such as green coconut fiber. Therefore, this work developed biocatalysts using waste as a support for immobilization, aiming for application in the synthesis of biodiesel via transesterification of residual frying oil. Lipase from Candida antarctica type B (CALB), Pseudomonas fluorescens (PFL) and Eversa lipase (EL) were chosen due to the heterogenicity of the substrate (oils). The use of enzymatic and co-immobilized mixtures has shown an advantage in the production of biodiesel. A solution of each lipase (0.05 mg/mL) was placed in contact with green coconut fiber (FC) (pretreated with steam explosion to increase surface area and facilitate interaction) to perform immobilization. The immobilization yields and recovered activity of the biocatalysts FC-PFL, FC-CALB and FC-EL showed that the individual immobilization of each lipase on coconut fiber was efficient. The biocatalysts obtained were subjected to chemical modifications post-immobilization with polyethylenimine (PEI), producing biocatalysts with FC-CALB-PEI, FC-PFL-PEI and FC-EL-PEI. Afterwards, treatment with glutaraldehyde (GLU) was carried out to produce enzyme-support covalent bonds, followed by modification with PEI, producing FC-CALB-GLU-PEI, FC-PFL-GLU-PEI and FC-EL-GLU- PEI. Through the characterization of these three categories of biocatalysts, the results showed that the predominant interactions between enzyme-support are predominantly hydrophobic, immobilization and coatings with GLU and PEI increased the thermostability of the lipases used and the presence of the covalent bond was observed by difference in the band pattern in the electrophoresis gel. For the application of these biocatalysts in the synthesis of biodiesel, the maximum enzyme load that can be immobilized in green coconut fiber was determined to be 5 mg/g for CALB biocatalysts, 10 mg/g for PFL and EL. In 5h of transesterification of residual frying oil, the FC-EL-GLU-PEI, FC-PFL-GLU-PEI and FC-CALB-GLU-PEI biocatalysts showed efficiency in reducing the acid number similar to the soluble enzyme. These results highlight the potential for the application of immobilized lipases in biodiesel production.