Recovery of valuable peptides from marine protein hydrolysate by electrodialysis with ultrafiltration membrane: impact of ionic strength

• Solution controlled conductivity regulates constant peptide migration rate.
• Ionic strength increase in solution increases UF membrane (UFM) negative charge.
• UFM negative charge enlarges its pore sizes and reduces the hydration layer.
• Ionic strength increases migration of Arginine and Lysine containing peptides.

Electrodialysis with ultrafiltration membrane (EDUF) has been used to selectively separate and concentrate peptides from protein hydrolysates. Therefore, comprehension and optimization of electrodialytic parameters involved in electrodialysis with ultrafiltration membrane (EDUF) are crucial for its industrial application. The aim of the present work was to study the effect of KCl concentrations (1, 3 and 5 g/L) in recovery compartment on local electric field (LEF), total charge transport, energy consumption, peptide migration rate and selectivity during EDUF of snow crab by product hydrolysate (SCBH). The highest peptide migration rate (13.76 ± 3.64 g/m2.h) with the lowest relative energy consumption (132.85 ± 15.67 W.h/g) was recovered for the first time to our best knowledge in EDUF process whatsoever the KCl conditions. Furthermore, constant LEF and linear peptide migration rate were obtained for all the conditions tested by regulating the conductivities to their initial values during the EDUF process. More than 85% of total peptides in KCl fractions had molecular sizes that ranged from 300 to 600 Da. In addition, KCl fractions were enriched with cationic peptides containing arginine and lysine and/or free arginine (Arg) and lysine (Lys). Furthermore, the relative abundance of Arg increased by 48%, 99% and 114% and that of Lys by 87%, 150% and 180% respectively in 1, 3 and 5 g/L KCl concentrations in comparison to SCBH. An increase in ionic strength amplified the negative charge density of UF membrane. This increase in negative charge density would induce (1) an increase in effective pore size due to the electrostatic repulsion between ions and (2) a thinner hydration layer due to salting out effect at pore walls.