Lactic acid bacteria fermentation improves the physicochemical properties, bioactivity, and metabolic profiles of lychee pulp

Lactiplantibacillus plantarum NCU0011259 was employed to ferment lychee pulp, with a systematic investigation of the flavor and bioactivities of the resulting product in this study. Results showed that fermentation with this strain increased organic acids, reduced sugars and bitter amino acids to refine taste, and elevated favorable alcohols/ethers while lowering off-flavor aldehydes to optimize the aroma profile. Moreover, fermentation induced profound metabolic remodeling, remarkably enhancing the in vitro antioxidant capacity and inhibitory activities against pancreatic lipase, α-glucosidase, and α-amylase. Correspondingly, the total polyphenol content increased from 321.94 μg/g to 663.75 μg/g, accompanied by notable enrichment of free polyphenols (e.g., (−)-gallocatechin) and restructuring of bound polyphenol fractions. Correlation analysis identified key polyphenols (e.g., m-coumaric acid, ferulic acid, tiliroside) as core components underlying enhanced antioxidant and digestive enzyme inhibitory activities. This study validates L. plantarum NCU0011259's excellent fermentation performance and lays a solid theoretical basis for developing high-quality fermented lychee functional foods. • LAB fermentation improved the bioactivity of lychee pulp. • LAB positively affected the flavor of lychee pulp. • Important metabolic compounds of LAB fermentation were identified. • LAB fermentation of lychee pulp has potential hypoglycemic and obesity-relieving effects. • Polyphenol changes are the key metabolites behind antioxidant differences.