Khadi fermentation

Khadi is the popular traditional alcoholic beverage in rural households in Botswana. The product It is produced by fermentation of Grewia flava (Malvaceaea) fruits supplemented with brown table sugar. Despite its popularity, its growing consumer acceptance, its potential nutritional value, and its contribution to the socio-economic lifestyle of Batswana, the production process remains non-standardised. Non-standardized production processes led to discrepancies in product quality and safety as well as varying shelf life. Identification of unknown fermentative microorganisms of khadi is an important step towards standardization of its brewing process for entrance into commercial markets. The aim of this study was to isolate and identify bacteria and yeasts responsible for fermentation of khadi. Yeasts and bacteria harboured in 18 khadi samples from 18 brewers in central and Northern Botswana were investigated using classic culture dependant technique and DNA sequencing methods. Additionally, we used the same techniques to investigate the presence of bacteria and yeasts on six batches of dried G. flava fruits used for production of the sampled brews. Our results revealed that Saccharomyces cerevisiae closely related to a commercial baker’s yeast strain sold locally was the most predominant yeast species in khadi suggesting a non-spontaneous brewing process. However, we detected diverse non-Saccharomyces yeasts, which are not available commercially in retail shops in Botswana. This also suggests that spontaneous fermentation is also responsible for fermentation of khadi. This study, presenting the first microbiological characterization of a prominent traditional alcoholic beverage in Botswana, is vital for development of starter cultures for the production of a consistent product towards the commercialization of khadi.