How plant species origin, identity, and cereal type shape the microbial composition and functional properties of Munkoyo, a traditional fermented beverage.

Traditional fermented cereal products are important for food security and nutrition. In Zambia and neighbouring countries, Munkoyo is a traditional beverage produced by spontaneous fermentation of cooked grains inoculated with roots from specific wild plant species ("Munkoyo" plants). These plants host distinct root endosphere microbial communities that also vary across geographic locations. However, how plant species identity, geographic origin, and cereal type shape the microbial composition and functional properties of Munkoyo remains unclear. We conducted fermentation experiments to assess how plant species, field location, and cereal type affect the bacterial communities and functional properties of Munkoyo. Fermentation with different co-occurring plant species showed distinct acidification dynamics, with Rhynchosia insignis yielding lowest final pH and Eminia holubii showing faster acidification. These differences were accompanied by distinct Munkoyo bacterial communities, primary metabolites, and aroma profiles. Using R. insignis from three districts showed that geographic origin significantly influenced titratable acidity, aroma composition, and microbial community structure and metabolic potential, indicating terroir effects. In contrast, cereal type (maize vs. sorghum) had a limited impact on final pH but altered microbial community composition and metabolic profiles. Overall, plant species identity and geographic origin are key determinants of microbial and functional variation in Munkoyo beverage.