Phospholipase A(2)-catalyzed hydrolysis of lecithin in a continuous reversed-micellar membrane bioreactor

Lysophospholipids and free fatty acids produced by lecithin hydrolysis are important natural compounds with high potential for application in the food, chemical, and pharmaceutical industries. In this work, the enzymatic hydrolysis of lecithin (essentially phosphatidylcholine) catalyzed by porcine pancreatic phospholipase A(2) (phosphatide 2-acyl-hydrolase, EC 3.1.1.4), encapsulated in mixed reversed micelles of lecithin and bis(2-ethylhexyl) sodium sulfosuccinate (AOT) in isooctane, was carried out in a continuous reversed-micellar membrane bioreactor. A tubular ceramic membrane with a 10,000 molecular weight (MW) cutoff was installed in an ultrafiltration module to retain the phospholipase A(2) (MW 14,000) and to continuously separate the products from the reaction media. Water and co-factor (Ca++)-cantaining reversed micelles of lecithin/AOT in isooctane were supplemented to the reactor to compensate for the permeation of reversed micelles and to continuously supply the substrate. The influence of relevant parameters, such as substrate, AOT and enzyme concentrations, water content and fluid hydrodynamics, on the performance of the ultrafiltration membrane bioreactor was investigated. Fluid axial velocity and substrate concentration were the major factors that affected the transport processes through the membrane. Permeate flow rate increased significantly with fluid axial velocity and decreased with substrate concentration; on the other hand, water and enzyme concentrations were identified as critical parameters for the final conversion of lecithin. The relationship between productivity and normalized residence time was analyzed for each set of experimental parameters tested. Operational stability of the bioreactor was tested in a long-term operation to confirm the high stability of this catalytic system.