Eco-friendly production of trimethylolpropane triesters from refined and used soybean cooking oils using an immobilized low-cost lipase (Eversa>® Transform 2.0) as heterogeneous catalyst

Abstract

Trimethylolpropane triesters – TMPTEs (biolubricants) have been produced through enzymatic hydroesterification of refined soybean (RSO) or used soybean cooking (USCO) oils. In the first step, enzymatic hydrolysis has been performed using a crude free lipase extract from Candida rugosa (CRL) to produce free fatty acids (FFAs). Complete hydrolysis of the oils was achieved after 3 h of reaction. Then, 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. High enzyme loaded biocatalysts (immobilization yield above 85%) were obtained for all lipase preparations using an initial protein loading of 40 mg g−1. Then, free lipases (liquid or powder forms) or immobilized biocatalysts were employed to produce TMPTEs via enzymatic esterification of the produced FFAs with trimethylolpropane (TMP) in eco-friendly processes (solvent-free systems). The new heterogeneous biocatalyst prepared in this study (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 at 55 °C, TMP:FFA ratio of 1:3.25, 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 as biocatalyst. Immobilized Eversa® Transform 2.0 retained above 90% of its original activity after 13 consecutive reaction cycles. The produced TMPTEs presented good cold temperature properties (pour point values between −11 and −9 °C).