Xu_2012_J.Biotechnol_162_407

A two-stage enzymatic process for producing fatty acid ethyl ester (FAEE) in a packed bed reactor is reported. The process uses an experimental immobilized lipase (NS 88001) and Novozym 435 to catalyze transesterification (first stage) and esterification (second stage), respectively. Both stages were conducted in a simulated series of reactors by repeatedly passing the reaction mixture through a single reactor, with separation of the by-product glycerol and water between passes in the first and second stages, respectively. The second stage brought the major components of biodiesel to 'in-spec' levels according to the European biodiesel specifications for methanol-based biodiesel. The highest overall productivity achieved in the first stage was 2.52 kg FAEE(kg catalyst)- h- at a superficial velocity of 7.6 cm min-, close to the efficiency of a stirred tank reactor under similar conditions. The overall productivity of the proposed two-stage process was 1.56 kg FAEE(kg catalyst)- h-. Based on this process model, the challenges of scale-up have been addressed and potential continuous process options have been proposed.