Use of nanofiltration membranes for the desalting of peptide fractions from whey protein enzymatic hydrolysates

Abstract

The performance of nanofiltration membranes for the desalting of a peptide mixture from tryptic hydrolysate ofwhey proteins containing 0.5 molL-1 sodium chloride has been investigated. Membranes are consisting of a strongly negatively charged material (MWI5, MG 17, BQOl, B006, B007) or of a polyamide (MX07) layered onto a polysulfone support. A satisfactory desalting of the whey protein tryptic hydrolysate has been obtained with ail membranes under study bath for dead-end and cross-flow filtration. The most suitable membrane for desalination was MX07, providing the highest permeability for salt and the lowest loss of peptidic materia1. For an membranes, RP-HPLC analysis of the permeates obtained in dead-end filtration revealed the presence of6 different peptidic sequences from ~-lactoglobulin (~-lg), but in a low amount Il %). The peptides found in the permeates are characterized by a net charge of 0 or + 1, while other peptides of similar molecular weight but containing negatively charged amino acid residues (Glu, Asp) remain in the retentates. Furthermore, it has been demonstrated that, compared to dead-end filtration, cross-flow filtration results in higher ion-peptide selectivities and less membrane fouling.