Genomic and metabolic characterization of defined starter cultures for safe and more consistent production of Ethiopian honey wine ("Tej").

Abstract

"Tej" is an Ethiopian wine made from honey and leaves or stems of Rhamnus prinoides, also known as "Gesho" in Amharic. It is spontaneously fermented, which leads to quality issues, affecting not only consistency but also safety. In this study, we aimed to address these challenges by developing a mixed starter culture containing safe microorganisms isolated from traditionally fermented "Tej" and honey in Ethiopia. Two-hundred-five lactic acid bacteria and yeast strains from "Tej" and honey samples were isolated, and phenotypic as well as molecular identification were performed. Among the yeasts, Saccharomyces cerevisiae was predominant. Among the lactic acid bacteria, Lacticaseibacillus paracasei was the most common. Controlled fermentations were conducted using combinations of L. paracasei and S. cerevisiae, followed by sensory analysis and characterization of volatile compounds. Fourteen flavor active compounds were identified. Of which ethyl-acetate, ethyl-nonanoate, 3-methyl-1-butanol, and acetaldehyde were dominant representatives of acetate ester, ethyl ester, higher alcohol and carbonyl compound, respectively. Genomic analysis showed that the selected L. paracasei strains lack plasmid-associated antimicrobial resistance genes, virulence factors, and transferable genetic elements, indicating they are safe. Overall, we conclude that using a defined starter culture can produce safer and higher-quality "Tej".