Membrane fractionation of a β-lactoglobulin tryptic digest: Effect of the membrane characteristics

BACKGROUND: Membrane separation technologies seem to be one of the best available techniques to fractionate protein hydrolysates containing bioactive peptides and obtain peptide fractions with increased functionality. The influence of the molecular weight cut-off (MWCO) of the membrane and its hydrophilic/hydrophobic characteristics on the fractionation of a β-lactoglobulin tryptic hydrolysate were studied in this research work in order to obtain more purified peptidic fractions. RESULTS: The molecular weight of the solutes, their charge and, ultimately, their hydrophobicity influenced peptide transmission. As regards the composition of the active layer of the membrane, high permeate flux values were maintained throughout the pH working range (from pH 4.0 to pH 10.0) when an extremely hydrophilic membrane was employed, even in the presence of peptide aggregates at acidic pH values. In addition, the decrease in the MWCO of the membrane (from 5 kDa to 1 kDa) did not improve the selectivity of the fractionation process, however, it assumed a significant decrease of the permeate flux through the membrane. CONCLUSION: The low efficiency of the process in terms of peptide recovery and the poor separation observed between bioactive and non-bioactive peptides work against the use of extremely hydrophilic membranes to fractionate peptide hydrolysates.