Bacterial succession, functional organization, and ecological drivers during spontaneous ukwa (Treculia africana) fermentation

Spontaneous fermentation of ukwa (Treculia africana) involves complex microbial succession that remains poorly characterized. Here, bacterial community dynamics during ukwa fermentation were resolved across six time points using high-throughput 16S rRNA gene sequencing. Fermentation followed a structured, stage-wise trajectory, beginning with plant-associated aerobic taxa, transitioning through a mid-phase dominated by fermentative firmicutes, and culminating in late-stage enrichment of acid-tolerant lactic and acetic acid bacteria. Microbial richness increased progressively during fermentation, while community composition clustered by time and correlated strongly with declining pH and moisture. Multivariate analyses identified these physicochemical gradients as primary drivers of succession. Network analysis further revealed distinct co-occurrence modules, indicating coordinated microbial guilds that underpin functional transitions during fermentation. This study provides the first sequencing-based ecological framework for ukwa fermentation and highlights how environmental filtering and microbial interactions shape community assembly in traditional African solid-state fermentations. These insights provide a basis for improving process control and guiding future starter culture development for ukwa and related fermented foods.