Innovative and Sustainable Use of Polyphenols from Macroalgae as Antioxidants in Aquaculture Nutrition

Oxidations are natural biochemical processes regulated by antioxidants. Problems arise with excessive oxidation or insufficient availability of antioxidants. In aquaculture, synthetic antioxidants are traditionally added to fish feed. These antioxidants are crucial for achieving high-quality fish feed, shelf life, and good fish health. In 2017, the most commonly used synthetic antioxidant, ethoxyquin, was banned in the EU. Other synthetic antioxidants are also being phased out due to safety concerns and consumer demand for products without synthetic additives. Natural antioxidants from plants and algae have therefore gained increased attention in the aquaculture sector. Norway has a significant but underutilized resource in macroalgae. Seaweed contains compounds with promising antioxidant properties but is less studied compared to land-based plants. Research on seaweed as a source of natural antioxidants is therefore a new field. By developing new uses for seaweed, we can create economic opportunities and strengthen Norwegian industry. In this research project, we investigate the most potent source of natural antioxidants in seaweed, polyphenols. We will use newly established methods to quantify and characterize these at the molecular level in selected algae harvested by the Norwegian industry. The project also aims to evaluate their use in aquaculture feed to improve fish health and feed protection. By focusing on polyphenols from macroalgae, harvested and cultivated in Norway, we can enhance the sustainability of aquaculture and contribute to global sustainability and economic growth.

The aquaculture sector faces many challenges worldwide, a very important one being the detrimental effects of oxidative stress in fish caused mainly by intensive production practices. Synthetic antioxidants, such as BHT, BHA and, until 2017, ethoxyquin, are used as feed additives to limit lipid oxidation, prevent oxidative losses of microingredients, and stabilize nutrients that are susceptible to critical oxidation. However, there are many safety concerns regarding these synthetic compounds and there is an urgent need to find more natural and healthier alternatives. Natural antioxidants (NAOX), such as polyphenols, are found in many healthy foodstuffs and have attracted the attention of the aquaculture industry for the development of innovative and attractive nutritional feeds, especially for their antioxidant and antimicrobial properties. Bioactive compounds from marine sources, such as seaweeds, are a promising source of NAOX as they are a readily available resource in Norway, a more natural food source for fish than terrestrial plant alternatives, and provide a unique selection of potent polyphenols. Examples of compounds from seaweeds that have already been reported to exhibit antioxidant properties include; phlorotannins, found only in brown algae, and laminarin, fucoxanthin, and fucoidan. These products are already being marketed, however, the potential of seaweeds as a sources of NAOX is only just being realised and needs warrants much further research. This project aims to study and optimize the extraction of NAOX from Norwegian seaweeds for use in fish nutrition to improve the oxidative status of the fish. The proposal is divided into 3 work packages: -Extraction and refinement of the quantity and quality of NAOX from selected species of seaweed -Develop methods for identification and quantification of NAOX from seaweed -Functionality testing (evaluating product performance) of a refined NAOX extract from seaweed using in vitro and in vivo approaches.