Metagenomic analysis of dominant lactic acid bacteria and yeast and starter culture formulation for injera sourdough fermentation

Injera, a fermented traditional flatbread made from teff, is the primary staple food consumed daily by most Ethiopian. However, the fermentation process is still spontaneous, resulting in product quality variation from batch to batch, household to household, and location to location. In this study, we aimed to evaluate the Lactic acid bacteria and yeast diversity of injera sourdough, particularly, to isolate, and assess their fermentation potential and formulate a defined starter culture. From the metagenomic analysis we found out that Fructilactobacillus sanfranciscensis and Kazachstania humilis were the dominant lactic acid bacteria (LAB) and yeast species, respectively, found in sourdough samples. Furthermore, there was significant variation in microbial composition both within and between regions. Besides LAB, in some sampling areas, acetic acid bacteria (AAB), specifically Acetobacter pomorum, Acetobacter orientalis , and Acetobacter fabarum , were predominantly found in Bahir Dar and Debre Berhan, which has not been reported in previous studies. Additionally, based on fermentation capacity, we isolated and screened LAB and yeasts from injera sourdough samples in different sites between regions and sample sites. Among the isolated species, four LABs and five yeast isolates were found with a good fermentation capacity. The fermentation ability of the combined LAB and yeast isolates were tested. After 48 hours of fermentation using a combination of LAB and yeast isolates, the quality of injera was tested by selected panelists. The results showed significant differences in flavor, aroma, texture, color, and injera quality. The best-performing combinations, based on the quality attributes ranked by the panelists, were the LAB and yeast combinations AD1 (LAB) + BD2 (yeast) and DB2 (LAB) + GO1 (yeast) + BD9 (LAB) isolates.