Desenvolvimento de um processo enzimático para a produção de biolubrificantes a partir de óleo de soja refinado e de fritura.

Abstract

In this study, trimethylolpropane triesters – TMPTEs (biolubricants) have been produced by a two-step enzymatic hydroesterification process using refined soybean (RSO) or used soybean cooking (USCO) oils as starting materials. In the first step, enzymatic hydrolysis was performed catalyzed by a crude free lipase extract from Candida rugosa (CRL) to produce free fatty acids (FFAs) in an emulsifier-free system. Complete hydrolysis of the oils were achieved after 3 h of reaction at 40 °C, using 3.2 g/L of CRL, mechanical agitation using an overhead motor stirrer at 1500 rpm and oil/water mass ratio of 40% and 50% for USCO and RSO, respectively. After, CRL, and the lipases from Thermomyces lanuginosus (Lipolase ® 100L and Eversa ® Transform 2.0) and Pseudomonas fluorescens (Amano AK) were immobilized via interfacial activation on polystyrene-divinylbenzene (PSty-DVB) beads. The immobilization procedure has been performed by mixing crude lipase extracts with 5 mM buffer sodium acetate at pH 5.0 for 18 h of contact under mechanical stirring (200 rpm) using a fixed protein loading of 40 mg/g of support. High enzyme loaded biocatalysts (immobilization yield above 85%) were obtained for all lipase preparations. Then, free lipases (liquid or powder forms) or immobilized biocatalysts were used to produce TMPTEs via enzymatic esterification of the produced FFAs with trimethylolpropane (TMP) in solvent-free systems. According to results, the highest activity in olive oil emulsion hydrolysis at pH 8.0 and 37 ºC was observed when using Lipolase ® 100L (255.9 ± 3.9 U/g). On the other hand, immobilized Eversa ® Transform 2.0 was the most active biocatalyst in TMPTEs production and maximum OH conversion of ≈97% using both FFA sources was achieved after 4 h of reaction conducted in open reactors in order to eliminate the formed water during the reaction at 55 °C, TMP:FFA molar ratio of 1:3.25 (0.77 g TMP – 5.74 mmol; 5.23 g FFA – 18.77 mmol), mechanical stirring rate of 240 rpm, and 15% of mass of biocatalyst per mass of starting materials. Under similar conditions, OH conversion of ~25% after 5 h of reaction was obtained using Novozym ® 435, a commercial immobilized lipase widely used in biotransformation reactions. Immobilized Eversa ® Transform 2.0 retained above 90% of its original activity after 13 consecutive reaction batches of 4 h each using both FFA from RSO and USCO as starting materials. The produced TMPTEs presented good cold temperature properties (pour point values between –11 and –9 °C). These esters also exhibited similar kinematic viscosity values at 40 ºC – 36.6 mm 2 /s for TMPTEs from RSO and 34.4 mm 2 /s for TMPTEs from USCO. These results show that Eversa ® Transform 2.0 immobilized via interfacial activation on PSty-DVB particles can also be an interesting option as heterogeneous biocatalyst to catalyze the production of synthetic esters with lubricant properties in industrial processes due to its high catalytic activity and reusability.