Enzymatic Synthesis of Ethyl Esters from Waste Oil Using Mixtures of Lipases in a Plug-Flow Packed-Bed Continuous Reactor

This work describes the continuous synthesis of ethyl esters via enzymatic catalysis on a packed-bed continuous reactor, using mixtures of immobilized lipases (combi-lipases) of Candida antarctica (CALB), Thermomyces lanuginosus (TLL), and Rhizomucor miehei (RML). The influence of the addition of glass beads to the reactor bed, evaluation of the use of different solvents, and flow rate on reaction conditions was studied. All experiments were conducted using the best combination of lipases according to the fatty acid composition of the waste oil (combi-lipase composition: 40% of TLL, 35% of CALB, and 25% of RML) and soybean oil (combi-lipase composition: 22.5% of TLL, 50% of CALB, and 27.5% of RML). The best general reaction conditions were found to be using tert-butanol as solvent, and the flow rate of 0.08 mL min(-1). The combi-lipase reactors operating at steady state for over 30 days (720 h), kept conversion yields of similar to 50%, with average productivity of 1.94 g(ethyl esters) g(substrate)(-1) h(-1), regardless of the type of oil in use. (C) 2018 American Institute of Chemical Engineers