Kombucha fermentation of upcycled Salvia officinalis enriched with honey and bee pollen: Phytochemical characterization, bioaccessibility of phenolics, and sustainability assessment

This study investigated whether kombucha fermentation could serve as a sustainable biotechnological strategy for the utilization and valorization of sage (Salvia officinalis) supercritical fluid extraction byproduct (So-SFE_BP) while enhancing its functional properties through supplementation with honey and bee pollen. During the fermentation process, strong and statistically significant correlations (p < 0.05) were observed between the main representative microbial populations (yeasts and acetic acid bacteria) and key physicochemical parameters, including pH, total titratable acidity (TTA), and reducing sugars, emphasizing the close relationship between microbial growth and biochemical transformations throughout the investigated fermentation period. The pH decreased from 6.90±0.01 to 2.78±0.03, reaching values considered safe for consumption, while TTA increased from 0.25±0.02 to 8.72±0.10 g AAE/L, with the highest acidity observed in formulations supplemented with bee products. Following pasteurization, the sage-based kombucha beverages maintained stable physicochemical characteristics, phenolic content, and antioxidant activity throughout the 12-week storage period. Selected formulations were subsequently evaluated through in vitro gastrointestinal digestion, revealing changes in measurable phenolic content and antioxidant capacity under simulated digestive conditions. Chromatographic characterization identified flavan-3-ols as the predominant phytochemicals, with (+)-epicatechin, epicatechin gallate, and epigallocatechin representing the major constituents. Computational ADME analysis predicted high gastrointestinal absorption for 76% of the identified compounds, while 12% were predicted to penetrate the blood-brain barrier (BBB) and avoid cellular efflux mechanisms, indicating their potential for central nervous system exposure. Sustainability assessment indicated that the proposed production chain was largely in alignment with green processing principles, although further optimization could improve its overall environmental performance. This study demonstrates that So-SFE_BP can be successfully transformed into a nutritional and functional pasteurized fermented beverage, with stable phytochemical characteristics, providing a sustainable strategy for agro-industrial byproduct valorization.