Novel Synbiotic Yogurt Formulation Supplemented with Fucoidan from Phaeophyceae Algae to Promote Limosilactobacillus reuteri and Lacticaseibacillus rhamnosus GG

Allergy is recognized as a public health problem with pandemic consequences and is estimated to affect more than 50% of Europeans in 2025. Prebiotic and probiotic food implementation has recently emerged as an alternative strategy to promote immunomodulatory beneficial effects in allergic patients. Among prebiotics, <i>Phaeophyceae</i> algae represent a niche of research with enormous possibilities. The present study aims to evaluate the in vitro prebiotic potential of fucoidan from <i>Fucus vesiculosus</i>, <i>Macrocystis pyrifera</i>, and <i>Undaria pinnatifida</i> algae, to promote the growth of <i>Limosilactobacillus reuteri</i> and <i>Lacticaseibacillus rhamnosus</i> GG as probiotic bacteria added to the formulation of a novel yogurt. Concentrations of fucoidan of 100 and 2000 µg/mL were added to reference growth media and kinetic growth curves for both microorganisms were fitted to the Gompertz equation. Optimized prebiotic conditions for fucoidan were selected to validate in vitro results by means of the formulation of a novel fermented prebiotic yogurt. Conventional yogurts (including <i>Streptococcus thermophilus</i> and <i>Lactobacillus delbrueckii</i> subs. bulgaricus) were formulated with the different fucoidans, and production batches were prepared for <i>L. rhamnosus</i> and <i>L. reuteri</i>. Increased <i>L. reuteri</i> and <i>L. rhamnosus</i> populations in 1.7-2.2 log₁₀ cycles just after 48 h of in vitro exposure were detected in fucoidan supplemented yogurt. <i>M. pyrifera</i> and <i>U. pinnatifida</i> fucoidans were the most effective ones (500 µg/mL) promoting probiotic growth in new formulated yogurts (during the complete shelf life of products, 28 days). Diet supplementation with fucoidan can be proposed as a strategy to modulate beneficial microbiota against allergy.