Microbiology and Biochemistry of Duma: Fermented Honey Drink of Southern Sudan

Abstract

Duma is a fermented honey drink commonly found in southern Sudan. Ethanol content of collected samples ranged from 4.3% to 10.2%, and total acidity ranged from 0.73% to 1.08%, while volatile fatty acids were very low. Laboratory fermentation showed that duma fermentation is an alcoholic fermentation as shown by an increase in yeast count producing 8.25% ethanol. The fermentation is also a lactic fermentation, which is indicated by the increase in lactic bacteria dropping the pH from 4.9 to 3.02. During the process total acidity increased from 0.12% to 0.8%. Tentative identification of microorganisms showed that yeast isolates belonged to Schizosaccharomyces pombe, Schizosaccharomyces octosporus, and Saccharomyces cerevisiae, while lactic acid bacteria belonged to Lactobacillu brevis, L. fermentum, L. plantarum and Pediococcus damnosus. Microorganisms that were responsible for fermentation were used as starter culture in laboratory fermentation. The result indicated that fermentation by this method is faster than the traditional fermentation. Metabolic products were characterized by an increase in ethanol to 9.86% and a total acidity of 0.75%. The pH dropped from 4.7 to 3.0, and volatile fatty acids were very low.Physiological studies have shown that yeast isolates were thermophilic and osmotolerant. With respect to salt tolerance, all isolates were able to grow at 10% sodium chloride.