The comparative ability of four isolates of Bacillus subtilis to ferment soybeans into dawadawa

Abstract

In an attempt to develop starter cultures for fermenting soybeans into the traditional West African condiment dawadawa, four isolates of Bacillus subtilis: 24BP2, 72RP17, 72BP30, and FpdBP2, which had been selected from 42 Bacillus cultures in a previous study by the current authors, were used separately to produce soy-dawadawa. The accompanying microbiological and biochemical changes, including enzymatic activities, as well as the organoleptic quality of the products were evaluated including that of a control sample which was fermented spontaneously. Significant differences existed in the ability of the four isolates to hydrolyse the soybean proteins, starch, and fat to produce dawadawa. Bacillus subtilis 24BP2 recorded the highest protease and amylolytic activities, 101 U/ml and 26.68 mg/ml, respectively, and liberated the most amino acids, 117.64 mg/g dry wt., during fermentation. Bacillus subtilis 24BP2 also grew to the highest population of cells in the final product. Taste panelists found soybean dawadawa produced by each of the four isolates acceptable and rated soup flavoured with soy-dawadawa produced by Bacillus subtilis FpdBP2 as the best sample. Panelists scored it higher than the control sample and soy-dawadawa produced by Bacillus subtilis 24BP2 in that order