The aquaculture industry generates substantial side streams from fish processing, including heads, frames, skin and viscera, which are frequently underutilised or discarded as waste. A recent study by Jenssen et al. (2025) – within the EcoeFISHent research project, in Horizon Europe – investigates the potential of upcycling these residual materials from sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) into high-value functional ingredients through enzymatic hydrolysis and subsequent membrane fractionation. This approach aligns with circular economy principles by converting food loss and waste (FLW) into protein-rich products with diverse applications in food, nutraceutical and cosmeceutical formulations (Dondero et al., 2025).
The valorisation of fish processing by-products represents a critical opportunity for enhancing resource efficiency while reducing environmental impact. Previous research has demonstrated that enzymatic hydrolysis can release bioactive peptides with various functionalities, including antioxidant, antihypertensive and wound-healing properties (Kaushik et al., 2024; Ucak et al., 2021). The present study builds upon this foundation by employing a systematic approach to characterise both the techno-functional attributes and biological activities of protein hydrolysates derived from pre-processed aquaculture side streams.
Methodology
The investigation employed pre-processed biomass from sea bream and sea bass, which had been dehydrated using an industrial process patented by Themis, a partner of the EcoeFISHent research consortium, to reduce moisture content and facilitate storage. The material was subjected to enzymatic hydrolysis using Corolase® 8000 at 65°C for one hour, with a 1:2 biomass-to-water ratio. Following hydrolysis and centrifugal separation, the resulting hydrolysate was divided into three fractions: a crude sample (unfractionated), and two fractions obtained through tangential flow filtration with a 3 kDa molecular weight cut-off (MWCO) membrane, yielding permeate (smaller peptides) and retentate (larger peptides) fractions (Jenssen et al., 2025).
Comprehensive characterisation encompassed proximate composition analysis, amino acid profiling, size exclusion chromatography for peptide size distribution, and colour analysis using CIELab coordinates. Techno-functional properties evaluated included foaming capacity and stability, emulsifying activity and stability indices, and oil binding capacity. The biological activity screening comprised seven distinct assays: angiotensin-converting enzyme (ACE) inhibitory activity, cellular antioxidant capacity, anti-inflammatory potential, anti-osteoporotic capacity, hepatoprotective effects, and wound healing activity on human keratinocyte cells (Jenssen et al., 2025).
Chemical composition and structural characteristics
All three samples exhibited remarkably high protein content, exceeding 80% as determined by Kjeldahl analysis, with the retentate demonstrating the highest value at 86.2%. Size exclusion chromatography revealed expected molecular weight distributions: the retentate possessed the highest average molecular weight (1771.5 Da), followed by the crude (1063.0 Da) and permeate (710.0 Da). Amino acid analysis indicated that glutamic acid and glycine were the most abundant residues, consistent with previous studies on sea bass and sea bream hydrolysates (Jenssen et al., 2025; Valcarcel et al., 2020).
The retentate fraction displayed elevated concentrations of collagen-associated amino acids (hydroxyproline, proline and glycine) compared to other fractions, suggesting enrichment in structural proteins. Colourimetric analysis revealed that the permeate exhibited significantly higher lightness (L* = 65.81) compared to the crude and retentate samples, which both displayed brown-reddish hues attributed to astaxanthin and oxidised myoglobin. ATR-FTIR spectroscopy confirmed that the retentate maintained a more organised and stable protein structure, with prominent amide bands indicating higher molecular weight peptides and more defined secondary structures (Jenssen et al., 2025).
Techno-functional properties
The retentate demonstrated superior techno-functional characteristics, excelling in emulsifying activity, foaming capacity and oil binding capacity. These properties correlate with its higher molecular weight profile, as larger peptide fractions can form more cohesive interfacial layers around oil droplets and gas bubbles (Aluko & Monu, 2003; Celus et al., 2009). The retentate’s enhanced performance suggests considerable potential for applications in food formulations requiring functional protein ingredients, particularly in products where emulsification and foaming properties are critical.
Conversely, the permeate fraction exhibited the lowest foaming capacity and both foaming and emulsifying stability, corresponding to its lower molecular weight distribution. However, the crude sample displayed the highest stability for maintaining foam and emulsion over time, potentially due to its mixed molecular weight distribution allowing more effective interface stabilisation (Jenssen et al., 2025). These findings underscore the importance of fractionation in tailoring hydrolysates for specific functional applications, as molecular weight significantly influences physicochemical behaviour (Yesiltas et al., 2023).
Biological activities
The bioactivity screening revealed selective functional properties across the fractions. ACE inhibitory activity, relevant for antihypertensive applications, was demonstrated by all samples, with the crude exhibiting the lowest IC₅₀ value (5.74 mg/mL), followed by retentate (6.56 mg/mL) and permeate (10.63 mg/mL). These values, while higher than those reported in some previous studies on sea bass and sea bream extracts, may reflect synergistic effects of multiple bioactive peptides present in the complex hydrolysate mixtures (Jenssen et al., 2025; Valcarcel et al., 2020).
The cellular antioxidant assay revealed that the permeate achieved approximately 45% oxidation inhibition at 1 mg/mL, the highest activity amongst the samples tested. This finding aligns with previous research indicating that lower molecular weight fractions typically exhibit enhanced cellular uptake and antioxidant capacity (Wang et al., 2019; Wolfe et al., 2008). The hepatoprotective assay demonstrated that both permeate and retentate significantly reduced fatty acid accumulation in liver cells at 0.2 mg/mL, suggesting potential applications in metabolic health formulations (Jenssen et al., 2025).
Wound healing potential
The most pronounced findings emerged from the wound healing assay, where the permeate fraction exhibited remarkable activity. At all tested concentrations (0.05, 0.025 and 0.015 mg/mL), the permeate significantly enhanced wound closure in human keratinocyte cells, achieving approximately 500% wound closure compared to control at 0.025 mg/mL. This exceptional performance suggests considerable potential for dermatological and cosmeceutical applications (Jenssen et al., 2025). The crude sample also demonstrated wound healing capacity at the lowest concentration (0.015 mg/mL), reaching approximately 550% wound closure.
The relationship between peptide size and wound healing activity has been documented in previous research, with smaller peptides generally demonstrating enhanced cellular penetration and biological activity (Huang et al., 2018; Woonnoi et al., 2021). The permeate’s superior performance in this assay, coupled with its increased cell viability at all tested concentrations (reaching approximately 150% at 0.015 mg/mL), highlights its potential as a safe and effective ingredient for skin regeneration applications (Jenssen et al., 2025).
Limitations and negative findings
The study revealed that none of the samples exhibited anti-inflammatory activity in lipopolysaccharide-stimulated macrophages or anti-osteoporotic capacity in osteoblast/osteoclast proliferation assays. These findings contrast with some previous research on sea bass and sea bream hydrolysates, which may be attributable to differences in tissue composition, as the present study utilised mixed side streams rather than specific tissues such as skin or heads (Chotphruethipong et al., 2021; de la Fuente et al., 2022).
The hepatoprotective results, while promising, require cautious interpretation as they were based on single biological experiments, necessitating further validation through additional replicates and potentially in vivo studies. The retentate demonstrated cytotoxic effects on keratinocytes at all tested concentrations, limiting its potential for topical applications despite its superior techno-functional properties. This highlights the importance of comprehensive safety evaluation alongside functional characterisation when developing ingredients for specific applications (Jenssen et al., 2025).
Conclusions and implications
This comprehensive investigation demonstrates that enzymatic hydrolysis and membrane fractionation represent effective strategies for converting aquaculture side streams into valuable functional ingredients with tailored properties. The retentate fraction’s superior techno-functional characteristics position it as an excellent candidate for food applications requiring emulsifying, foaming and oil-binding properties. Conversely, the permeate’s exceptional wound healing capacity, combined with enhanced cell viability and cellular antioxidant activity, suggests promising applications in nutraceutical and cosmeceutical formulations (Jenssen et al., 2025).
The findings support the development of sustainable bioprocessing approaches aligned with circular economy principles in aquaculture. By transforming processing waste into high-value ingredients, the industry can simultaneously address environmental concerns and create new revenue streams. Future research should focus on identifying specific bioactive peptide sequences responsible for the observed activities, conducting clinical trials to validate wound healing efficacy, and exploring synergistic combinations of fractions to optimise both functional and biological properties. The successful valorisation of aquaculture side streams represents a crucial step towards more sustainable and resource-efficient food systems (Dondero et al., 2025; Kaushik et al., 2024).
#EcoeFISHent #Wasteless
Dario Dongo
Cover art copyright © 2025 Dario Dongo (AI-assisted creation)
References
- Aluko, R. E., & Monu, E. (2003). Functional and bioactive properties of quinoa seed protein hydrolysates. Journal of Food Science, 68(4), 1254–1258. https://doi.org/10.1111/j.1365-2621.2003.tb09635.x
- Celus, I., Brijs, K., & Delcour, J. A. (2009). Fractionation and characterization of brewers’ spent grain protein hydrolysates. Journal of Agricultural and Food Chemistry, 57(13), 5563–5570. https://doi.org/10.1021/jf900626j
- Chotphruethipong, L., Binlateh, T., Hutamekalin, P., Sukketsiri, W., Aluko, R. E., & Benjakul, S. (2021). Hydrolyzed collagen from defatted sea bass skin and its conjugate with epigallocatechin gallate: In vitro antioxidant, anti-inflammatory, wound-healing and anti-obesity activities. Food Bioscience, 43, Article 101303. https://doi.org/10.1016/j.fbio.2021.101303
- de la Fuente, B., Pinela, J., Calhelha, R. C., Heleno, S. A., Ferreira, I. C. F. R., Barba, F. J., Berrada, H., & Barros, L. (2022). Sea bass (Dicentrarchus labrax) and sea bream (Sparus aurata) head oils recovered by microwave-assisted extraction: Nutritional quality and biological properties. Food and Bioproducts Processing, 136, 97–105. https://doi.org/10.1016/j.fbp.2022.09.004
- Dondero, L., Tardanico, F., Lertora, E., & Boggia, R. (2025). Unlocking the potential of marine sidestreams in the blue economy: Lessons learned from the EcoeFISHent project on fish collagen. Marine Biotechnology, 27, Article 63. https://doi.org/10.1007/s10126-025-10438-9
- Huang, C.-Y., Wu, T.-C., Hong, Y.-H., Hsieh, S.-L., Guo, H.-R., & Huang, R.-H. (2018). Enhancement of cell adhesion, cell growth, wound healing, and oxidative protection by gelatins extracted from extrusion-pretreated Tilapia (Oreochromis sp.) fish scale. Molecules, 23(10), Article 2406. https://doi.org/10.3390/molecules23102406
- Jenssen, M., Sone, I., Grasso, F., Turrini, F., Tardanico, F., Atanasio, G. D. N., Paz, D. M., Sobrado, R. V., Martínez, M. M. A., Boggia, R., Grasselli, E., & Lian, K. (2025). Valorization of aquaculture side streams from sea bream and sea bass by enzymatic hydrolysis and fractionation: Chemical and biological insights. Frontiers in Nutrition, 12, Article 1663294. https://doi.org/10.3389/fnut.2025.1663294
- Kaushik, N., Falch, E., Slizyte, R., Kumari, A., Khushboo, Hjellnes, V., Carvajal, A. K., & Mozuraityte, R. (2024). Valorization of fish processing by-products for protein hydrolysate recovery: Opportunities, challenges and regulatory issues. Food Chemistry, 459, Article 140244. https://doi.org/10.1016/j.foodchem.2024.140244
- Ucak, I., Afreen, M., Montesano, D., Carrillo, C., Tomasevic, I., Simal-Gandara, J., & Barba, F. J. (2021). Functional and bioactive properties of peptides derived from marine side streams. Marine Drugs, 19(2), Article 71. https://doi.org/10.3390/md19020071
- Valcarcel, J., Sanz, N., & Vázquez, J. A. (2020). Optimization of the enzymatic protein hydrolysis of by-products from seabream (Sparus aurata) and seabass (Dicentrarchus labrax), chemical and functional characterization. Foods, 9(10), Article 1503. https://doi.org/10.3390/foods9101503
- Wang, X., Yu, H., Xing, R., Liu, S., Chen, X., & Li, P. (2019). Preparation and identification of antioxidative peptides from Pacific herring (Clupea pallasii) protein. Molecules, 24(10), Article 1946. https://doi.org/10.3390/molecules24101946
- Wolfe, K. L., Kang, X., He, X., Dong, M., Zhang, Q., & Liu, R. H. (2008). Cellular antioxidant activity of common fruits. Journal of Agricultural and Food Chemistry, 56(18), 8418–8426. https://doi.org/10.1021/jf801381y
- Woonnoi, W., Chotphruethipong, L., Tanasawet, S., Benjakul, S., Sutthiwong, N., & Sukketsiri, W. (2021). Hydrolyzed collagen from Salmon skin increases the migration and filopodia formation of skin keratinocytes by activation of FAK/Src pathway. Polish Journal of Food and Nutrition Sciences, 71(3), 323–332. https://doi.org/10.31883/pjfns/141515
- Yesiltas, B., García-Moreno, P. J., Mikkelsen, R. K., Echers, S. G., Hansen, D. K., Greve-Poulsen, M., Sørensen, A.-D. M., & Jacobsen, C. (2023). Physical and oxidative stability of emulsions stabilized with fractionated potato protein hydrolysates obtained from starch production side stream. Antioxidants, 12(8), Article 1622. https://doi.org/10.3390/antiox12081622
Dario Dongo, lawyer and journalist, PhD in international food law, founder of WIISE (FARE - GIFT - Food Times) and Égalité.
