DEVELOPMENT OF A BIOACTIVE BEVERAGE FROM UNDERUTILISED AFRICAN LEGUMES THROUGH FERMENTATION WITH A MULTIFUNCTIONAL INDIGENOUS LACTOCOCCUS LACTIS

Introduction: The growing demand for sustainable functional foods has intensified interest in plant-based fermented beverages enriched with naturally occurring bioactive compounds. Underutilised African legumes, particularly Bambara groundnut (Vigna subterranea) and African yam bean (Sphenostylis stenocarpa), possess excellent nutritional and bioactive quality but remain neglected due to limited value-addition. Fermentation with systematically selected indigenous lactic acid bacteria (LAB) offers an effective strategy for improving their nutritional, technological, and functional attributes.

Objectives: This study investigated the bioactive and probiotic potentials of indigenous LAB isolated from spontaneously fermenting Bambara groundnut and African yam bean milks and evaluated the suitability of the most promising strain as a starter culture for developing a functional yoghurt-like beverage from a Bambara groundnut (BGN)–African yam bean (AYB) milk blend.

Methodology: LAB were isolated from spontaneously fermenting legume milks and screened for techno-functional and probiotic potentials, including proteolytic activity, acid (pH 2.5–3.5) and bile salt (0.3–0.5%) tolerance, auto-aggregation, and antioxidant activity, using DPPH and hydroxyl radical scavenging assays. The best-performing isolate was identified by 16S rRNA gene sequencing and employed as a starter culture for controlled fermentation of BGN–AYB (1:1) milk. Changes in microbial growth, pH, titratable acidity, and antioxidant activity during fermentation were determined using standard microbiological and physicochemical methods. Values (n=3) were subjected to one-way ANOVA and compared for significant differences using Tukey’s HSD test (p < 0.05).

Results: Spontaneous fermentation promoted LAB growth to approximately 8.0 log CFU/mL after 24 h. The isolates predominantly exhibited proteolytic activity, while selected strains showed excellent survival under simulated gastrointestinal conditions, recording tolerance to acidic pH (77–100%) and bile salts (46–100%). Auto-aggregation ranged from 48–72%. Extracellular metabolites exhibited substantial antioxidant activities, with DPPH radical scavenging ranging from 43.54–56.14% and hydroxyl radical scavenging from 46.8–81.7%. Based on its combined technological and functional performance, isolate AYB2463 was selected and identified as Lactococcus lactis. Controlled fermentation with this strain significantly acidified the legume beverage (pH 5.94 to 3.76), increased titratable acidity (0.264 to 0.714 g/L), supported microbial growth, and enhanced DPPH radical scavenging activity from 69.34% to 72.19%.

Discussion: The findings demonstrate that indigenous Lactococcus lactis AYB2463 functions as an effective bioactive starter culture capable of improving the physicochemical quality, probiotic characteristics, and antioxidant potential of beverages derived from underutilised African legumes. This highlights the value of indigenous microbial biodiversity in functional food innovation.

Conclusions: This study demonstrates the feasibility of transforming neglected African legumes-Bambara groundnut and African yam bean into a sustainable, dairy-free functional beverage through controlled fermentation with a multifunctional indigenous Lactococcus lactis. The resulting product combines desirable probiotic potentials with enhanced antioxidant activity, supporting its potential as a novel source of bioactive compounds and a promising functional beverage.