Síntese enzimática de biolubrificantes a partir de óleos vegetais e óleo fúsel, utilizando enzimas imobilizadas em compósito de lignina do bagaço de caju

Abstract

The environmental impacts of petroleum-based lubricants have sparked growing interest in the search for more sustainable alternatives. In this context, biolubricants emerge as a promising option, available from both synthetic and renewable sources. Among these, fatty acids extracted from vegetable oils stand out, conferring biodegradable properties and lower environmental toxicity to lubricants compared to mineral-based lubricants. Therefore, several strategies for biolubricant synthesis have been explored, including the use of biocatalysts. In this context, this study had two main objectives: i) to evaluate the production of fatty acids by enzymatic hydrolysis catalyzed by lipase from Rhizomucor miehei, targeting future applications; and ii) to evaluate the synthesis of biolubricants using free fatty acids (FFAs) obtained by chemical hydrolysis in combination with fusel oil, a waste product from the sugar and alcohol industry, as an alcoholic source. Initially, enzymatic hydrolysis studies of commercial soybean, canola, sunflower, and cottonseed oils were carried out by R. miehei lipase in its free form and immobilized on a magnetic support obtained from cashew apple bagasse lignin (Lig- Mag), for the production of free fatty acids. For this purpose, lignin was initially extracted from cashew apple bagasse, followed by the magnetization process and subsequent immobilization of the enzyme, evaluating two enzyme loads: 0.5 mg and 5 mg of protein per g of support, in which the obtained biocatalysts were named Lig- Mag_RML_0.5 and Lig-Mag_RML_5, respectively. In the hydrolysis tests, oil: water molar ratios of 1:1, 1:2, and 1:3 were evaluated at 50 °C, 150 rpm, for 24 h. As a result, it was observed that the highest hydrolysis percentages were obtained with cottonseed and canola oils, and the biocatalyst Lig-Mag_RML_5 presented the best performance, obtaining a hydrolysis percentage of 62.2 ± 1.8% for cottonseed oil and 53.4 ± 1.4% for canola oil. Subsequently, a study was carried out to evaluate the efficiency of the lipase B enzyme from Candida antarctica, in its free form and immobilized on the Lig-Mag support (Lig-Mag_CALB), in the esterification reaction using FFAs obtained by chemical hydrolysis and fusel oil as an alcohol mixture. The reactions occurred at acid: alcohol molar ratios of 1:1 and 1:3, at temperatures of 40 °C and 50 °C, for 48 h at 150 rpm. In the reactions conducted using Lig-Mag_CALB, the highest conversions were obtained with a 1:1 molar ratio and a temperature of 40 °C, reaching conversions of 72.4±1.3% and 73.9±0.6% using FFAs from cottonseed oil and canola oil, respectively. The biocatalyst showed satisfactory operational stability, reaching relative conversions of 66.8% with FFAs from cottonseed oil and 64.5% with FFAs from canola oil, after five evaluated cycles. Furthermore, when stored at 4 °C, it maintained 85% of its catalytic activity after 27 days. Both biolubricants obtained from canola 9 and cottonseed oils showed promising physicochemical properties, meeting the technical requirements for lubricant formulations. Therefore, enzymatic hydrolysis constitutes a viable alternative for obtaining free fatty acids, while transesterification presents itself as an efficient strategy for the synthesis of esters with lubricating properties. The use of residues such as fusel oil and cashew apple bagasse lignin contributes to the

development of more sustainable processes, with the potential to generate biodegradable, non-toxic products and add value to industry by-products.