Bioréacteur enzymatique couplé à l'ultrafiltration pour la valorisation des co-produits issus des industries de la pêche. Application à la seiche Sepia officinalis

This work is conducted in the framework of cuttlefish Sepia officinalis by-products up-grading from conditioning industries. It concerns the implementation of the enzymatic hydrolysis and the membrane separation processes to obtain valuable compounds such as peptides and lipids. The techniques used in this study belong to "clean technologies", environmentally sound involving moderate investment and low energy consumption. Hydrolysis of cuttlefish viscera had been carried out in two steps. The first one had the objective to determine the efficiency of the enzymes on the matrixes investigated as well as the study area. Once the enzyme had been chosen, the second step was to optimize enzymatic hydrolysis using experimental designs, in order to obtain the highest small peptides recoveries the soluble phase and an antimicrobial activity. The fractionation on the protein hydrolysate according to the charge upon ion exchanging columns allowed determining the ionic profile of the antimicrobial peptides. Membrane fractionation (ultrafiltration) was then used as a second lever to act (i) on size distribution of peptides and (ii) on the activity level of the hydrolysates. First, small-scale fractionation was carried out on polyethersulfone and regenerated cellulose membranes with molecular weight cut-offs ranging from 1000 to 100 000 Da. Then, an scaling-up methodology was investigated by ultrafiltration of the hydrolysate on a pre-industrial pilot plant. The originality of this PhD work is (i) the enrichement of cuttlefish viscera hydrolysates with valuable compounds such as essential amino acids and the enhancement of the antimicrobial activity and (ii) the possibility to up-scale enzymatic hydrolysis and ultrafiltration integrating them in the conception of a complete industrial process.