Manuel Marrero

Macroalgal wracks can be considered unpleasant for beach users and, consequently, they are usually collected from most touristic beaches and discarded. However, seaweeds are an important source of bioactive lipid compounds, such as phospholipids, glycolipids, and n-3 polyunsaturated fatty acids (n-3 PUFA), displaying multiple health-promoting properties, including antioxidant and antimicrobial activities. The aim of this study is to characterize the lipid composition of twelve marine seaweed species (two green, six red, and four brown species) from macroalgal wracks of Gran Canaria Island, and to evaluate their potential use for several purposes, including human and animal nutrition. Lipid content, lipid classes, and fatty acid profiles of isolated specimens from the macroalgal wracks were determined. Lipid contents ranged between 0.27 and 3.17% of dry weight, with all species showing high phytosterols proportions and balanced omega-6/omega-3 (n-6/n-3) ratios. In addition, Cymopolia barbata, Asparagopsis sp., and Hypnea spinella seem to be an attractive source of both mono- and di-galactosyl-diacylglycerols, while A. stellata, Jania sp., and Lobophora sp. are relatively rich in n-3 LC−PUFA. Finally, both green algae showed the most favorable values for the nutritional indicators of cardiovascular health promotion. Overall, the macroalgal species analyzed could be considered as interesting sources for human and animal nutrition.

Macroalgae have been recently described as a potential ingredient for aquafeeds, exerting several physiological benefits. Grass carp (Ctenopharyngodon idella) is a freshwater species, which has been the major fish species produced in the world in the last years. In order to determine the potential use of macroalgal wracks in fish feeding, C. idella juveniles were fed with an extruded commercial diet (CD) or the CD supplemented with 7 of a wind dried-powder (1mm) from either a multispecific macroalgal wrack (CD+MU7) or a monospecific macroalgal wrack (CD+MO7) obtained from Gran Canaria island (Spain) coasts. After 100 days of feeding, survival, fish weight, and body indexes were determined, and muscle, liver, and digestive tract samples were collected. The total antioxidant capacity of macroalgal wracks was analyzed by assesing the antioxidant defense response and digestive enzymes activity in fish. Finally, muscle proximate composition, lipid classes (LC), and fatty acid (FA) profiles were also studied. Our results suggest that dietary inclusion of macroalgal wracks does not have negative effects on growth, proximate, and lipid composition, antioxidative status, or digestive capacity of C. idella. In fact, both macroalgal wracks caused a general lower fat deposition, and the multispecific wrack enhanced catalase activity in the liver.

Fish vary in their ability to biosynthesise long-chain polyunsaturated fatty acids (LC-PUFA) depending upon the complement and function of key enzymes commonly known as fatty acyl desaturases and elongases. It has been reported in Solea senegalensis the existence of a Δ4 desaturase, enabling the biosynthesis of docosahexaenoic acid (DHA) from eicosapentaenoic acid (EPA), which can be modulated by the diet. The present study aims to evaluate the combined effects of the partial replacement of fish oil (FO) with vegetable oils and reduced environmental salinity in the fatty acid composition of relevant body compartments (muscle, hepatocytes and enterocytes), the enzymatic activity over α-linolenic acid (ALA) to form n-3 LC-PUFA through the incubation of isolated hepatocytes and enterocytes with [1-¹⁴C] 18:3 n-3, and the regulation of the S. senegalensis fads2 and elovl5 in the liver and intestine. The presence of radiolabelled products, including 18:4n-3, 20:4n-3 and EPA, provided compelling evidence that a complete pathway enabling the biosynthesis of EPA from ALA, establishing S. senegalensis, has at least one Fads2 with ∆6 activity. Dietary composition prevailed over salinity in regulating the expression of fads2, while salinity did so over dietary composition for elovl5. FO replacement enhanced the proportion of DHA in S. senegalensis muscle and the combination with 20 ppt salinity increased the amount of n-3 LC-PUFA in hepatocytes.