Screening of a feruloyl esterase-producing lactobacillus strain and its application in citrus whole-fruit pulp fermentation: organic acids, volatile compounds, and sensory evaluation.

Feruloyl esterase (FAE)-producing lactobacillus strains were selected from the citrus whole-fruit pulp after 48 h of fermentation. Among them, Lactiplantibacillus plantarum K33 showed the highest ferulic acid (FA) producing ability. Using citrus whole-fruit pulp as the fermentation matrix, physicochemical, compositional, and sensory outcomes were compared between pulps fermented by K33 and by the commercial strain L. plantarum N13 (Lp-N13). After fermentation, K33 increased total acidity, lowered pH, and markedly raised FA concentration and total phenolic content (TPC). Fermentation also altered other organic acids and volatile profiles: L-malic acid decreased significantly, whereas lactic and succinic acids increased. Terpenes remained predominant, with a significant rise in the relative proportion of alcohols. KEGG analysis showed that the differential of organic acids was mainly associated with arginine biosynthesis and other pathways. Sensory evaluation indicated enhanced lactic acid flavor and reduced citrus-peel aroma. Overall, K33 shows promise for fermentation of functional plant-based beverages.