Application of ultrafiltration membranes for purification of structured phospholipids produced by lipase-catalyzed acidolysis

The possibilities of applying ultrafiltration for the purification of structured phospholipids (PLs) produced by lipase-catalyzed acidolysis in a hexane system were examined. Commercial polymeric membranes with different cut-offs (1000–20,000 Da) were screened for their abilities to separate free fatty acids (FFA) from structured PLs. Suitable membranes were selected in terms of high selectivity between FFA and PLs. Several membranes showed to be able to reject more than 90% of phosphatidylcholine (PC), however, based on the solubility parameters of the polymers many of the membranes would not be suitable for long term with the solvents in use. One membrane was more stable with the solvents compared with the other membranes screened; it was a polysulphone (PSf) membrane on polyester (PE) support (GR70PE). GR70PE showed similar retention of PC as that of few other membranes, but showed relatively higher retention of FFA, resulting in lower selectivity. Increased pressure increased the retention of both PC and FFA, however, the selectivity was improved. With a discontinuous diafiltration process (11 batches) using GR70PE, it was possible to change the molar ratio between PC and FFA from 1:48 to 1:1.6. The results of this study show that membrane separation may be a promising route for downstream processing of structured PLs.