Lactobacillus caucasus LN6 Fermentation Improves Phenolic Profile and Antidiabetic Potential of Sea Buckthorn Juice

Fermentation is a promising biotechnological approach for enhancing the composition and biological functionality of bioactive compounds in fruit and vegetable matrices. Fermentation with Lactobacillus caucasus LN6 altered the polyphenol, organic acid, and volatile compound contents of sea buckthorn juice. Monosaccharide levels were reduced, and α-glucosidase inhibitory activity was increased. During simulated gastrointestinal digestion, phenolic compounds from both fermented (FSBJ) and non-fermented (NFSBJ) sea buckthorn juices were mainly released during the intestinal phase. However, fermented juice retained more phenolics, resulting in greater delivery to the colon and enhanced bioactivity. Oral administration of FSBJ significantly reduced fasting blood glucose levels in T2DM mice and improved dyslipidemia by reducing serum TC, TG, and LDL-C levels. FSBJ alleviated hepatic oxidative stress and improved liver injury. FSBJ significantly decreased Dubosiella, Bifidobacterium , and norank_o__Clostridia_UCG-014 , while increasing beneficial bacteria, such as Faecalibaculum, Akkermansia , and Lachnospiraceae_NK4A136_group . These changes improved the gut microbiota diversity and reshaped the community structure. The therapeutic efficacy of NFSBJ was significantly lower than that of FSBJ. Overall, these results indicate that fermentation alters the composition of bioactive compounds in sea buckthorn juice and enhances its hypoglycemic effect, demonstrating its potential for functional food development.