Fermentative Microbes of Khadi, a Traditional Alcoholic Beverage of Botswana

Khadi is a popular traditional alcoholic beverage in rural households in Botswana. The product is produced by fermentation of ripened sun-dried Grewia flava (Malvaceae) 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 Botswana, the production process remains non-standardized. Non-standardized production processes lead 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 harbored in 18 khadi samples from 18 brewers in central and northern Botswana were investigated using classic culture-dependent techniques and DNA sequencing methods. Additionally, we used the same techniques to investigate the presence of bacteria and yeasts on six batches of ripened-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 possible non-spontaneous brewing process. However, we also detected diverse non-Saccharomyces yeasts, which are not available commercially in retail shops in Botswana. This suggests that spontaneous fermentation is partially 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.

Woody vegetation change over more than 30 years in the interior duneveld of the Kalahari Gemsbok National Park

Background and objectives: Long-term studies of woody plants in South Africa are scarce. This study, initiated in the late 1970s, therefore aids understanding of vegetation dynamics in the southern Kalahari by investigating woody vegetation change at and away from a watering point. Methods: At three sites, all woody individuals were counted by species in plots 0.5 or 1 ha in size. Seedlings were noted separately from the >0.2 m group of individuals. Results: Vachellia erioloba and shrub density decreased over time whereas dwarf shrub species’ numbers fluctuated markedly. Additionally, no increase in density of known bush encroaching species (e.g. Grewia flava, Rhigozum trichotomum and Senegalia mellifera) was found in this large conservation area. Discussion and conclusion: The changes in density of the woody species seem to point to the importance of particular rainfall patterns or sequences of events over different years that are responsible for these changes in the southern Kalahari, and the evident lack of bush encroachment in this conservation area supports the notion that bush encroachment in arid savannas is driven primarily by land-use practices and not by elevated carbon dioxide levels that are sometimes provided as cause for encroachment.

Classification, description and mapping of the vegetation in Khutse Game Reserve, Botswana

There is currently no detailed classification and description of plant communities in Khutse Game Reserve (KGR), Botswana, using phytosociological techniques. The main aim of this study was to classify and describe plant communities in KGR. Classification and description of plant communities will help in understanding the plant ecology of KGR. Braun-Blanquet sampling method was applied in 91 stratified random relevés. Nine plant communities were identified and classified using Modified TWINSPAN which is contained in JUICE program. The results showed that there was a statistically significant difference in percentage cover of herbaceous plants between the different plant communities. Schmidtia pappophoroides-Stipagrostis uniplumis and Heliotropium lineare-Enneapogon desvauxii communities had higher cover (%) of herbaceous plants than other communities. Catophractes alexandri-Stipagrostis uniplumis community had the highest cover (%) of shrubs. There was no statistically significant difference in plant species diversity (Shannon-Wienner Index) and species evenness between plant communities, but there was a statistically significant difference in plant species richness between the different plant communities. Dichrostachys cinerea-Grewia flava community, Senegalia mellifera subsp. detinens-Maytenus species community and Catophractes alexandri-Stipagrostis uniplumis community had lower number of species, whereas Vachellia luederitzii var. retinens-Grewia flava community had the highest number (46) of plant species. This study will help the Department of Wildlife and National Parks (DWNP) to develop an updated and informed Management Plan for the reserve, which takes cognizance of the plant ecology of the reserve.

Morphological responses of woody species to simulated twig-browsing in Botswana

Increased shoot growth has recurrently been recorded following real or simulated shoot browsing, although responses may vary between different woody species. We investigated morphological responses to simulated dry-season browsing on Colophospermum mopane, Acacia tortilis, Grewia flava, Peltophorum africanum and Ziziphus mucronata, which differ in growth rate, occurrence of spines and use by mammalian herbivores. Treatment groups included a control, four clipping intensities and cutting at ground level. Responses were monitored during the following growth season on three annual shoots, located in the bottom, middle and top height interval, on each sapling. All five species showed compensatory growth responses, although no obvious relation was found between the strength of responses and growth rate or natural browsing pressure. The general pattern was an increased shoot length, shoot diameter, number of lateral shoots and shoot biomass with increased clipping intensity. These responses are probably an effect of the reduction of competing growing points and disrupted apical dominance. Growth responses were stronger in shoots with higher location on the sapling, which may reflect the pressure on saplings to attain a certain height to avoid browsing, reproduce and increase resistance to fire. We found no evidence of the number of spines being an induced defence in either of the two spinescent species studied.