Design of a New Chemoenzymatic Process for Producing Epoxidized Monoalkyl Esters from Used Soybean Cooking Oil and Fusel Oil

• Published in: Catalysts Vol. 13; no. 3; p. 543
• Main Authors: Mattos, Fernanda R., Júnior, José Miguel, Sabi, Guilherme J., Garcia, Pedro H. D., Carvalho, Patrícia O., Luiz, Jaine H. H., Mendes, Adriano A.
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.03.2023
• Subjects: Air pollution; Biocatalysts; Catalysts; Chemical reactions; chemoenzymatic process; Cooking; Divinylbenzene; Energy minerals; Environmental impact; Epoxidation; epoxidized monoalkyl esters; Esterification; Esters; Fatty acids; Formic acid; Fossil fuels; Fusel oil; Global temperature changes; Glycerol; Greenhouse gases; Hydrogen peroxide; Hydrolysis; Innovations; Lipase; Microorganisms; Molecular sieves; NMR; Nuclear magnetic resonance; Nuclear reactors; Oxygen content; Raw materials; Reaction time; Soybean; Vegetable oils; waste oil
• ISSN: 2073-4344; 2073-4344
• DOI: 10.3390/catal13030543

The aim of this study was to produce epoxidized monoalkyl esters (EMAE), a valuable class of oleochemicals used in a wide range of products and industries, from used soybean cooking oil (USCO) and fusel oil via a three-step chemoenzymatic process. This process consists of a first enzymatic hydrolysis of USCO to produce free fatty acids (FFA). Here, five microbial lipases with different specificities were tested as biocatalysts. Full hydrolysis of USCO was obtained after a 180 min reaction time under vigorous stirring (1500 rpm) using a non-specific lipase from Candida rugosa (CRL). Then, monoalkyl esters (MAE) were produced via the esterification of FFA and fusel oil in a solvent-free system using the lipase Eversa® Transform 2.0 (ET2.0) immobilized via physical adsorption on poly(styrenene-divinylbenzene) (PSty-DVB) beads as a biocatalyst. Different water removal strategies (closed and open reactors in the presence or absence of molecular sieves at 5% m.m−1) on the reaction were evaluated. Maximum FFA conversions of 64.3 ± 2.3% (open reactor after a 30 min reaction time) and 73.5 ± 0.4% (closed reactor after a 45 min reaction time) were observed at 40 °C, using a stoichiometric FFA:fusel oil molar ratio (1:1), without molecular sieves, and 5 mg of immobilized protein per gram of reaction mixture. Under these conditions, maximum FFA conversion was only 30.2 ± 2.7% after a 210 min reaction time in a closed reactor using soluble lipase. Reusability tests showed better retention of the original activity of immobilized ET2.0 (around 82%) after eight successive batches of esterification reactions conducted in an open reactor. Finally, the produced MAE was epoxidized via the Prilezhaev reaction, a classical chemical epoxidation process, using hydrogen peroxide and formic acid as a homogeneous catalyst. The products were characterized by standard methods and identified using proton nuclear magnetic resonance (1H NMR). Maximum unsaturated bond conversions into epoxy groups were at approximately 33%, with the experimental epoxy oxygen content (OOCexp.) at 1.75–1.78%, and selectivity (S) at 0.81, using both MAEs produced (open or closed reactors). These results show that this new process is a promising approach for value-added oleochemical production from low-cost and renewable raw materials.