Metabolomic insights reveal bioactive enhancement in fermented oat-based beverages via Lactobacillus plantarum

Abstract

This study evaluates the impact of thermal processing and fermentation with Lactobacillus plantarum on the bioactive composition and metabolic profile modulation of an oat-based (Avena sativa) beverage. A base beverage (OBB), a heattreated variant (OBB-H) and a fermented beverage (OBB-F) were produced. Processing-induced changes were monitored using global bioactivity indices, including total phenolic content (TPC) and antioxidant activity (IC₅₀), together with targeted chromatographic analyses and untargeted metabolomics by UHPLC-QTOF. Thermal treatment led to a significant increase in TPC, associated with the release of glycosylated phenolic compounds, including avenanthramides and hydroxycinnamic acids. In contrast, fermentation maintained TPC at comparable levels while reducing the IC₅₀ by 49.6%, indicating a substantial enhancement of antioxidant capacity. This improvement was linked to phenolic biotransformation processes that redistributed the phenolic pool towards compounds with greater functional contribution. Targeted analysis enabled the tracking of this reorganisation during fermentation, characterised by the consumption of hydroxycinnamic acids: ferulic, caffeic and p-coumaric; and the concomitant accumulation of lower-molecular-weight phenolic derivatives, notably protocatechualdehyde. Untargeted metabolomic analysis revealed a profound fermentation-driven reconfiguration of the metabolic profile, including the formation of oxylipins (9-HODE and 13-HODE), oxygenated fatty acids and lysophospholipids, as well as the emergence of lactoylated carbohydrate derivatives and exopolysaccharide fragments not previously reported in fermented oat beverages. In addition, the fermentative process resulted in a marked increase in phosphorylated nucleotides, such as inosine 5′-monophosphate, which is associated with umami taste enhancement, suggesting a potential positive impact on the sensory complexity of the product. Fermentation also promoted the consumption of aromatic amino acids and the generation of tryptophan-derived metabolites, including indole-3-lactic acid. Overall, these findings demonstrate that functional fermentation with L. plantarum acts as a key metabolic modulator, inducing specific biotransformations that preserve total phenolic content while amplifying antioxidant functionality and diversifying the bioactive profile of oat-based plant beverages.