Biochemical composition, antioxidant, and antimicrobial properties of fermented plant-based beverages from Ceratonia siliqua (Carob) supplemented with Thymus capitatus

Authors: Hamza Gadhoumi, Walid yeddes, Sawsen Selmi, Saber Khammassi, Salma N. Mohamed, Majdi Hammami, Mouna Ben Farhat, Moufida S. Tounsi, and El Akrem Hayouni

Ger. J. Vet. Res 2025. vol. 5, Iss. 4 pp:1-14
Doi: https://doi.org/10.51585/gjvr.2025.4.0159

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Abstract:

The growing interest in functional beverages has led to the exploration of plant-based formulations enriched with bioactive compounds. This study investigates the biochemical, antioxidant, antimicrobial, and volatile profile modifications resulting from the lactic fermentation of Ceratonia siliqua (carob) combined with the aromatic plant Thymus capitatus using two probiotic strains: Lactobacillus plantarum (LP) and Lactobacillus acidophilus (LA). The fermentation process led to a significant drop in pH (to ~3.5–4.0) and an increase in titratable acidity, with Lactobacillus acidophilus showing a more pronounced acidification capacity. Phenolic and flavonoid contents increased markedly, particularly in thyme-enriched samples, reaching up to 200 mg GAE/100 mL. Simultaneously, sugar content decreased, reflecting effective microbial metabolism. Volatile compound analysis via GC-MS revealed major fermentation metabolites (lactic acid, acetic acid, ethanol) and the presence of thymol and carvacrol in thyme-supplemented formulations, contributing to both sensory enhancement and biological activity. Antioxidant assays (DPPH, ABTS, and reducing power) confirmed the enhanced radical-scavenging capacity of fermented beverages, especially those fermented with Thymus capitatus and L. acidophilus, with IC₅₀ values comparable to those of synthetic standards. Antimicrobial activity was observed against both Gram-positive and Gram-negative pathogens, with inhibition zones up to 24 mm and MICs as low as 0.5 mg/mL in thyme-acidophilus samples. These effects are attributed to the synergistic action of organic acids and aromatic terpenes. Overall, the combination of aromatic plants and probiotic fermentation significantly improves the functional, antioxidant, and antimicrobial properties with promising applications in veterinary medicine as natural alternatives to promote gut health, enhance disease resistance, and reduce reliance on synthetic antimicrobials.

Keywords:

Antimicrobial properties, Antioxidant activity, Bioactive compounds, Functional beverages, Lactic acid bacteria, Plant-based beverages

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