Fermented Royal Jelly Enriched With 10‐Hydroxydecanoic Acid and Its Potential for Enhancing Mucosal Immunity

Royal jelly (RJ) is known to contain 10-hydroxydecanoic acid (10HDAA), which has been shown to have immune activation properties, including the promotion of M cell differentiation. However, the natural concentration of 10HDAA in RJ is relatively low. To enhance the functional use of RJ as an immunostimulatory food ingredient, this study aimed to increase its 10HDAA content using bacteria capable of converting 10-hydroxy-2-decenoic acid (10H2DA) to 10HDAA in RJ. A lactic acid bacterium, <i>Lactobacillus panisapium</i>, was isolated from the digestive tract of queen bees and demonstrated a high capacity to convert 10H2DA to 10HDAA. Using the isolated strain, fermented RJ (fRJ) with a fivefold increase in 10HDAA content was produced compared to raw RJ. Preliminary evaluations of fRJ's immune-stimulating effects revealed significant benefits, including enhanced M cell differentiation, activation of macrophage phagocytic ability, and increased immunoglobulin (Ig) A secretion in individuals with reduced salivary IgA levels. Safety assessments confirmed that fRJ is safe for consumption. In summary, fRJ enriched with 10HDAA was produced and demonstrated potential as an immune-stimulating food.