Enhancement in nutraceutical potential of legumes through lactic acid bacteria-mediated solid-state fermentation

Abstract

Aim: This study aimed to evaluate the potential of a lactic acid (LA) bacteria (LAB) co-culture during solid-state fermentation (SSF) of yellow peas and soybeans, with an emphasis on the production of health-promoting metabolites from legumes. Methods: A synergistic probiotic consortium comprisingL.acidophilus,L.plantarum, andL.rhamnosus was employed for SSF across 11 different legume substrates at three legume-to-water ratios over 48 h to identify optimal fermentation conditions. Based on microbial growth outcomes, yellow peas and soybeans were selected for further SSF studies at an optimized substrate-to-water ratio (1:3). Fermentation performance was assessed by monitoring microbial growth, pH changes, production of LA, short-chain fatty acids, B-vitamins, and antimicrobial activity. Data were statistically analysed using two-way ANOVA. Structural modifications of fermented substrates and bacterial colonization were examined using scanning electron microscopy (SEM). Results: SSF exhibited distinct substrate-specific biochemical patterns. Yellow peas supported rapid LAB proliferation (16.04 log₁₀ CFU/g) and pronounced acidification (pH 7.33→4.66), reflecting their high fermentable carbohydrate content. In contrast, soybean yielded higher LA production (7.28 g/L) despite lower viable counts, indicating enhanced per-cell metabolic activity. Short-chain fatty acid synthesis was also influenced by substrate composition and pH, with soybean showing maximum accumulation of acetic acid (11.73 g/L) and propionic acid (15.95 g/L). Butyric acid was detected at lower levels in both substrates. B-vitamin biosynthesis was also substrate-dependent: yellow peas produced higher levels of vitamin B₂ (7.097 µg/mL) and B₉ (3.69 µg/mL), whereas soybeans favoured vitamin B₁₂ synthesis (2.187 µg/mL). Fermented extracts exhibited strong antimicrobial activity againstEscherichiacoli,Salmonellatyphi, andStaphylococcusaureus, with inhibition zones reaching up to 28, 26, and 18.6 mm, respectively. SEM analysis revealed matrix erosion and aggregation of LAB colonization. Conclusions: SSF is an efficient and sustainable strategy for producing multifunctional probiotic-enriched fermented legumes with enhanced nutritional and antimicrobial properties.

Keywords

antimicrobial activity / B-vitamins / plant-based substrates / SCFAs / synergistic fermentation

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