Nutrient-related metabolomic profiling of Litopenaeus vannamei exposed to Lactococcus lactis D1813 under selected salinity and dissolved oxygen conditions

The efficacy of probiotic supplements in aquaculture is critically dependent on strain-specific functionality and synergistic interactions with environmental conditions. The present study investigated the effect of Lactococcus lactis D1813, varying levels of salinity (8 and 25 ppt), and dissolved oxygen (DO) levels of 8.5 and 3.5 mg/L on the metabolomic profiling of nutrients in Litopenaeus vannamei . Muscle samples of Litopenaeus vannamei were analyzed using UHPLC-tandem mass spectrometry for metabolomic characterization of nutrients. Among the results, fifty selected nutrient-associated metabolite features were annotated. The Probiotic + low salinity + high dissolved oxygen group (Huang) showed higher log 10 -transformed normalized peak intensity values for amino acid- and carbohydrate-related metabolites, including ethyl lysine, arginine, leucyl-leucine, methionine, glutamic acid, serine, proline, tyrosine, galactose, raffinose, glycogen, and glucose, with values of 6.23, 5.91, 5.88, 5.76, 5.44, 5.33, 5.16, 6.21, 6.09, 5.69, and 5.15, respectively, compared with the control group. Similarly, vitamin-associated metabolites showed higher log 10 -transformed normalized peak intensity values in the Probiotic + low salinity + high dissolved oxygen group (Huang), including niacin, cobalamin, folate, tocopherol, riboflavin, and thiamin, with values of 6.50, 6.51, 6.37, 6.49, 6.54, and 6.83, respectively. Likewise, among the results of the Kyoto Encyclopedia of Genes and Genomes (KEGG), the Huang group also identified significantly enriched pathways for amino acid, vitamin, lipid, and nucleotide metabolism. This study presents the novel function of Lactococcus lactis D1813 as a probiotic that enhances the metabolomic profile of Litopenaeus vannamei under specific environmental conditions. Our findings suggest that the inoculation of Lactococcus lactis D1813 (10 6 CFU/mL), along with the salinity and DO of 8 ppt and 8.5 mg/L, improved the metabolomic profile of nutrients in Litopenaeus vannamei.