DKI supplemented with Phaeo = DKI 1,3 β-glucan

β-glucans are a powerful, valuable and well-documented immunostimulant for improving immune status and enhancing disease resistance in farmed fish.

The diatom Phaeodactylum tricornutum is characterized by a high content of bioactive molecules,
such as the omega-3 fatty acid EPA, the carotenoid pigment fucoxanthin and chrysolaminarin, a water-soluble polysaccharide consisting of glucose monomers linked by a β-(1,3)-linkage with limited β-(1,6)-branching. Among the reported immunostimulatory effects of fish diets enriched with P. tricornutum the following can be mentioned: i) increase in the activity of the hemolytic complement, ii) stimulation of the phagocytic activity and the respiratory burst activity of leukocytes in the head kidneys, iii) increase in serum IgM levels, the main adaptive humoral response and usually the only immunoglobulin class described in fish, iv) increase in the expression of IL-8, a pro-inflammatory cytokine that contributes (in conjunction with IL-1 and TNFα) to the host defense mechanisms in response to invasions or bacterial colonization.

In addition, it has been shown that chysolaminarin-enriched extracts: i) stimulate the expression of chaperone hsp90aa and the antimicrobial peptide hamp1, thereby modulating the NF-kB pathway and pro-inflammatory cytokine production in macrophages, ii) modulate key immune genes, such as the glucan receptor c-type lectin (clec), interferon-related factors irf3 and irf7, TNFa, the chemokine cxc10, g-type lysozyme, cd4 and IL-1B, which has a supportive and immunomodulatory and anti-inflammatory effect, and iii) modulate the gut microbiome, thereby promoting bacteria of the genus
Vibrio is reduced.