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 i n the food, chemical, and pharmaceutical industries. In this work, the enzymatic hydrolysis of lecithin (essentially phosphatidylcholine) ca talyzed by porcine pancreatic phospholipase A(2) (phosphatide 2-acyl-h ydrolase, EC 3.1.1.4), encapsulated in mixed reversed micelles of leci thin and bis(2-ethylhexyl) sodium sulfosuccinate (AOT) in isooctane, w as 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 r eaction media. Water and co-factor (Ca++)-cantaining reversed micelles of lecithin/AOT in isooctane were supplemented to the reactor to comp ensate for the permeation of reversed micelles and to continuously sup ply the substrate. The influence of relevant parameters, such as subst rate, AOT and enzyme concentrations, water content and fluid hydrodyna mics, on the performance of the ultrafiltration membrane bioreactor wa s investigated. Fluid axial velocity and substrate concentration were the major factors that affected the transport processes through the me mbrane. Permeate flow rate increased significantly with fluid axial ve locity 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 produc tivity and normalized residence time was analyzed for each set of expe rimental parameters tested. Operational stability of the bioreactor wa s tested in a long-term operation to confirm the high stability of thi s catalytic system.