A hydroesterification reaction system to produce octyl esters using degummed soybean oil as substrate: Combining reusable free and immobilized lipases

This study shows the enzymatic synthesis of octyl alcohol-based biolubricants carried out in two catalytic steps: degummed soybean oil (DSO) hydrolysis and esterification of the produced and purified free fatty acids (FFA). Several lipases were evaluated as catalysts in the hydrolysis of DSO. Under optimal conditions, lipase from Pseudomonas fluorescens (PFL) yielded 97 % conversion after 23 h using 50 U/g oil and DSO:water mass ratio of 1:0.5. Sequential batch strategies have been developed for the recovery and reuse of free enzyme in further hydrolysis cycles. When hexane was used in the separation between the FFA-rich phase and the phase composed of water, enzyme and glycerol, there was better PFL recovery and FFA-conversion of 65 % was still achieved after five 24-hour hydrolytic cycles. In the esterification step, the potential of four lipases (commercial Lipozym-435, and lipase B from Candida antarctica (CALB), lipase from porcine pancreas (PPL) and Eversa® Transform 2.0 (EV) immobilized on Purolite Lifetech EC8806F) were evaluated in the production of octyl esters in a solvent-free medium (FFA/octanol molar ratio of 1:2.5) using screw-capped glass bottles as reactor. The immobilized EV gave the best ester yield (∼87 wt%). When EV-Purolite was used in a vortex flow reactor, a yield of around 94 wt% was reached after 3 h of reaction using a biocatalyst load of 1 % (w/v) and FFA/octanol molar ratio of 1:2.5. The immobilized lipase could be reused for five consecutive 3 h-batches of esterification, maintaining the octyl esters yield of the first batch.