Spontaneously fermented Allium cepa L. as a source of lactic acid bacteria with probiotic potential

Onions (Allium cepa L.) are widely recognized for their nutritional and medicinal properties. This study investigates the suitability of spontaneously fermented onions as a natural source of lactic acid bacteria (LAB) with probiotic potential. The isolated LAB were identified as Lactiplantibacillus plantarum, Lactiplantibacillus pentosus, and Levilactobacillus brevis. Comprehensive analysis were conducted to evaluate their ability to ferment various carbohydrates, enzymatic activity, resistance to environmental stressors (pH, bile salts, NaCl, H₂O₂, and phenol), and antimicrobial properties. Most strains demonstrated high survivability in acidic conditions (pH 3.0) and bile salts (0.4%), crucial for probiotic viability in the gastrointestinal tract, and exhibited antimicrobial activity against foodborne pathogens. These antimicrobial effects were primarily due to organic acid production, with hydrogen peroxide synthesis providing additional support. Additionally, none of the tested strains hydrolyzed mucin, confirming their safety for potential probiotic applications. These findings indicate that LAB from fermented onions could be promising candidates for application in probiotic and functional food formulations.