A study, in which the IRTA of the Government of Catalonia and the company PTAqua are also participating, shows that various natural extracts of terrestrial and marine origin, by transforming waste into useful resources, can act in a complementary manner: some providing antioxidant and antibacterial protection, whilst others strengthen the immune system
The Aquaculture Research Group (GIA) at the ECOAQUA University Institute, part of the University of Las Palmas de Gran Canaria (ULPGC), together with collaborators from the Institut de Recerca i Tecnologia Agroalimentàries (Institute for Agri-Food Research and Technology) IRTA and the company PTAqua, has demonstrated, in a recent study, the potential of various natural extracts derived from agricultural waste and marine biomass to improve the health of farmed fish in a more sustainable manner.
The finding was made as part of the doctoral thesis of Mr Luis Molina Roque, recipient of grant PRE2022-103656 funded by MICIU/AEI/10.13039/501100011033 and by the European Social Fund Plus (ESF+), and is being co-supervised by Professor Daniel Montero of the ULPGC and a researcher at the GIA, and Dr Silvia Torrecillas, a researcher at IRTA. This doctoral thesis is part of the ULPGC’s ACUISEMAR doctoral programme.
Aquaculture has become one of the world’s main sources of aquatic protein. As global fish consumption rises, so does the need to produce more food in a sustainable and safe manner. However, this growth brings with it significant challenges: infectious diseases, reliance on antibiotics, and environmental pressure resulting from intensive production.
ECOAQUA GIA researcher Luis Molina Roque during a moment in his research.
In this context, this study, published in the scientific journal ‘Frontiers in Marine Science’ under the title ‘Antioxidant, antibacterial, and immunostimulatory potentials of terrestrial and marine extracts from by-products and low-value biomass: an ex vivo study in gilthead seabream (Sparus aurata) head kidney leukocytes’, has explored a promising alternative: using agricultural waste and marine biomass as a source of natural compounds capable of improving fish health.
From waste to resource: circular economy and sustainability
In addition to its applications in aquaculture, the study highlights the value of utilising agro-industrial waste and marine biomass of low commercial value, which fits fully within the circular economy and sustainability model promoted by the European Union.
Much of the waste generated by the food industry still contains bioactive molecules of great biotechnological value. This is the case with fruit peels or certain types of seaweed with little commercial use. Instead of being discarded, these materials could be turned into functional ingredients for animal feed.
The idea is simple: transforming waste into useful resources. In this way, waste is reduced, local raw materials are utilised, and high value-added ingredients are generated for strategic sectors such as aquaculture.
The researchers selected nine different extracts: four of terrestrial origin and five of marine origin. The terrestrial plant by-products included extracts rich in compounds found in pomegranates, citrus flavonoids and grape seeds. The marine extracts included several species of seaweed and microalgae. The researchers analysed their antioxidant, antibacterial and immunostimulatory capacity in immune cells from gilthead seabream (Sparus aurata), one of the most important species in Mediterranean aquaculture. The results showed clear differences between the two groups.
On the one hand, terrestrial plant extracts exhibited high antibacterial activity and higher levels of phenolic compounds and flavonoids, molecules associated with potent antioxidant activity. This means they could help reduce oxidative stress in fish, a common problem in intensive farming systems.
A potential ally against pathogenic bacteria
One of the most significant findings of the study was, furthermore, the antibacterial capacity of some of these plant extracts, particularly those derived from pomegranate. These compounds were able to inhibit bacteria responsible for major diseases in aquaculture, such as Vibrio anguillarum, Vibrio harveyi and Photobacterium damselae subsp. piscicida.
The significance of this finding is considerable. For years, the aquaculture industry has been seeking sustainable alternatives to reduce the use of antibiotics, the excessive use of which contributes to the development of bacterial resistance.
Although the researchers caution that in vivo studies are still required before commercial application, the data obtained suggest that these natural extracts could form part of future preventive strategies in fish farming.
Algae activate the immune system
Meanwhile, whilst the plant extracts stood out for their antioxidant and antibacterial properties, several of the marine extracts used demonstrated a notable ability to modulate the immune response in fish.
Tests carried out on sea bream immune cells revealed that certain algae and microalgae were capable of stimulating defence mechanisms related to phagocytosis and peroxidase activity, processes essential for combating infections.
According to the authors, this suggests that marine compounds could help strengthen the immune system of fish, increasing their ability to respond to pathogens.
Furthermore, some of these species contain sulphated polysaccharides and other bioactive compounds known for their biological activity, opening up new possibilities for developing more effective functional feeds.
Next step
The researchers note that the next challenge will be to verify whether these effects observed in the laboratory are replicated in live fish and to determine which combinations and doses are most effective and safe.
One of the most interesting hypotheses is that terrestrial and marine extracts may act in a complementary manner: some providing antioxidant and antibacterial protection, whilst others bolstering the immune system.
The work also aligns with the ‘One Health’ approach, which recognises the connection between animal, human and environmental health, reducing the use of antibiotics, improving animal welfare and making use of waste – objectives that collectively contribute to more sustainable food systems. The study was conducted using in vitro and ex vivo methodologies, reducing the use of animals in research and aligning with European principles of responsible research and animal welfare.
The research, presented this week by Luis Molina Roque at the 20th National Aquaculture Congress held in Vigo, forms part of the LARVOOST project (PID2021-122474OB-I00), whose principal investigators are Professor Daniel Montero, a researcher at ECOAQUA’s GIA, and Dr Silvia Torrecillas, a researcher at IRTA. Funded by the Ministry of Science, Innovation and Universities, the State Research Agency and European Union ERDF funds, this project represents a further step towards more efficient, resilient and environmentally friendly aquaculture.