Abstract
Electrodialysis with ultrafiltration membrane (EDUF) was selected to separate a herring milt hydrolysate (HMH) in a scale-up and long-term study for the recovery of bioactive peptides. The scale-up was performed to maximise peptide recovery by placing a total membrane area of 0.08 m2 for each anionic and cationic compartment. Twelve consecutive runs were carried out, for a total of 69 h, with minimal salt solution cleaning in between experiments. The final peptide migration rate showed that cationic peptides had a higher average migration rate (5.2 ± 0.8 g/m2·h), compared to anionic peptides (4.7 ± 1.1 g/m2·h). Migration was also selective according to peptide identifications and molecular mass distribution where only small molecular weights were found (<1000 Da) in both recovery compartments. The areal system resistance slightly decreased during each run and the averaged values were stable in between experiments since they were all found in the 95% confidence interval. In addition, total relative energy consumption was quite consistent with an average value of 39.95 ± 6.47 Wh/g all along the 12 consecutive runs. Finally, according to membrane characterization, there was no visual fouling on the different membranes present in the EDUF cell after 69 h of treatment. This may be due to the salt cleaning in between experiments which allowed removal of peptides from the membranes, thus allowing recovering initial system working parameters at the beginning of each run. The entire process was revealed to be very consistent and repeatable in terms of peptide migration, global system resistance, and energy consumption. To the best of our knowledge, this is the first time such EDUF conditions (membrane surface, duration, and minimal salt cleaning between experiments) are being tested on a complex hydrolysate.
Highlights
In the past decades, electromembrane processes have widely been used to separate and concentrate bioactive peptides and to valorise by-products in the agri-food industry [1,2]
This means that a large proportion of peptides are still available for migration, but that the recovered fraction may be concentrated in bioactive peptides, and the specificity of the peptides separated is generally really high in comparison with other processes [4,10,11,15]
The opposite trend was observed for pH 9 (14.64 ± 0.95 g/m2·h for anionic and 7.81 ± 0.68 g/m2·h for cationic), and values were more similar at pH 6 with 10.81 ± 0.28 g/m2·h and 11.49 ± 2.51 g/m2 h for anionic and cationic recovery compartments, respectively
Summary
Electromembrane processes have widely been used to separate and concentrate bioactive peptides and to valorise by-products in the agri-food industry [1,2]. At lab scale, Henaux et al [10] used three UF membrane cut-offs (50, 20, and 5 kDa) for the separation of a salmon protein hydrolysate. They were able to achieve a maximum peptide migration rate of 3.19 ± 0.14 g/m2·h for the cationic recovery compartment, and that configuration generated a relative energy consumption (REC) of 512.56 ± 95.59 Wh/g. The molecular weight distribution of the peptide profiles revealed molecular weights lower than 1000 Da with a maximum between 300–500 Da. On the other hand, Durand et al [11,12], at lab scale, worked with two herring milt hydrolysates (one which was the same as in this study, namely, PG1), but with a double simultaneous separation (2 UF membranes of 20 and 50 kDa for cationic and anionic peptide recovery). The REC obtained for the entire stack, for initial hydrolysate (not mentioned for PG1) was 46.99 ± 6.59 Wh/g
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