Concentration and purification of blue whiting peptide hydrolysates by membrane processes

This study aims to evaluate the performances of the membrane processes during the treatment of blue whiting peptide hydrolysates.Ultrafiltration with high molecular weight cut-off (MWCO) can be used for the separation between peptides and non-hydrolyzed proteins. A membrane of MWCO 20 kDa was tested on hydrolysates containing 11.4 g of peptides per liter of solution. Steady fluxes were satisfactory (100 l/h/m2 at 12 bars and 15 °C) but the nitrogenized matter retention is approximately 30%, which leads to a considerable peptide loss in the permeate.In addition, ultrafiltration with intermediate MWCO is considered for the enrichment of fractions of peptides of a definite molecular weight range. Two membranes of MWCO 4 and 8 kDa were selected; allowing easy separation between peptides of high and low molecular weight. Moreover, they show variable rejection rates according to classes of molecular weight, which gives hope for a possible fractionation in the range of 1000–7000 Da.Lastly, the nanofiltration enables the concentration of peptides of low molecular weight by avoiding an excessive concentration of salts. The results with a membrane of MWCO 300 Da are very encouraging because the retention of peptides bigger than 1000 Da is total so that the concentration of the retentate up to about 300 g/l can be reached.