Valorization of marine side-streams through innovative green extraction techniques for the recovery of fish oil and protein hydrolysates

Introduction Fishing and aquaculture activities generate significant volumes of by-products during processing with great potential for valorization, mainly due to their high content in valuable components such as proteins and polyunsaturated fatty acids. In salmon, fat represents the major fraction on a dry basis, with significant levels of Omega-3 and Omega-6 fatty acids that can be extracted from heads and viscera for applications in the food, feed and cosmetic industries. In contrast, hake and shrimp by-products are mainly protein-rich, subjected to be hydrolysed into peptides with improved properties such as digestibility, bioactivity and functional technological applications. In alignment with the principles of circular economy, green extraction techniques such as supercritical CO2 and subcritical H2O can be used to recover high-purity lipid fractions without the use of conventional solvents. Likewise, the protein fraction can be valorised through fermentation processes using specific bacteria to obtain protein hydrolysates, with improved biological and technological functionalities. Material and methods Results Oil extraction: Response Surface Methodology (RSM) was used for both extraction techniques. Fermentation: Was carried out in 1-L glass bottles using a Bacillus subtilis strain with different protein and glucose concentrations. Conclusions: ▪Supercritical CO₂ oil extraction showed increased yields at higher pressures and temperatures. Fatty acid composition remained unchanged under all tested conditions. ▪Subcritical H₂O oil extraction showed significantly higher yields only at higher temperatures. Extraction time had no significant effect on yield. Fatty acid composition remained unchanged under all tested conditions. ▪Fermentation showed better yields when working at lower protein concentrations. As glucose affected the pH of the medium, pH control is needed to reach a more accurate conclusion in this case. This will be done soon in 5-L bioreactor experiments. •Supercritical CO₂ extraction •Subcritical H₂O extraction -1 +1 0 T40 60 50 °C P 200 550 375 bar -1 +1 0 T 120 200 160 °C t10 20 15 min Dried Salmon Fresh Salmon 11 experiments 11 experiments Valorization of marine side-streams through innovative green extraction techniques for the recovery of fish oil and protein hydrolysates Nuria Otero-Logilde1, Borja Lagoa-Costa1, Diego Méndez-Paz1, Rebeca Vázquez-Sobrado1, Martín RodríguezÁlvarez1, David Alonso Baptista de Sousa1 1Sustainability and Circular Economy Group, ANFACO-CYTMA, Vigo, Spain. FISH BYPRODUCTS FISH OIL? YES NO OIL EXTRACTION •Supercritical CO2 •Subcritical H2O FERMENTATION PROTEIN HYDROLYSATES CHARACTERIZATION: Salmon, Hake, Shrimp OIL Oil extraction: Oil quality was based on acidity and peroxide value (<5% and <11 meqO₂/kgfat). Fatty acid composition showed no significant differences across experiments (PUFA: 31–36% and ω-3: 11–14%). Objective: The present work aimed at the valorization of fish by-products through the extraction of oil from salmon heads using supercritical fluids and subcritical water, and the production of bioactive peptides through bacterial fermentation processes from protein-rich by-products such as hake and shrimp. ScCO2 Extraction yield P↓T→40 ˚C 50 ˚C 60 ˚C 550 bar 55% 60% 67% 375 bar 43% 49% 57% 200 bar 32% 39% 48% SubH2O Extraction yield t↓T→120 ˚C 160 ˚C 200 ˚C 20 min 15% 27% 44% 15 min 10% 18% 54% 10 min 5% 19% 54% B. subtilis Hake by-products Protein conc. (g/L) 20 40 Glucose conc. (g/L) 034.82% 6.96 g/L 9.81% 3.92 g/L 221.71% 4.34 g/L - B. subtilis Shrimp by-products Protein conc. (g/L) 20 40 Glucose conc. (g/L) 023.16% 4.63 g/L 9.97% 3.99 g/L 224.58% 4.92 g/L - 0% 10% 20% 30% 40% 024 48 72 Degree of hydrolysis Time (h) Hake by-products Hake 20 - 0 Hake 20 - 2 Hake 40 - 0 0% 10% 20% 30% 40% 024 48 72 Degree of hydrolysis Time (h) Shrimp by-products Shrimp 20 - 0 Shrimp 20 - 2 Shrimp 40 - 0