Characterization of the bacterial flora of Sudanese sorghum flour and sorghum sourdough

The microflora of a Sudanese sorghum flour, a spontaneously fermented sourdough and along-term sourdough produced in a Sudanese household by consecutive re-inoculations, wasstudied. The dominant contaminants of sorghum flour were Gram-negative, catalase-positive,rod-shaped bacteria with counts of about 10⁵ cfu g^?1. Thespontaneously fermented sorghum sourdough showed a bacterial succession from Gram-negative,catalase-positive contaminants to Enterococcus faecalis , Lactococcus lactis , Lactobacillus fermentum and Lact. reuteri . The total bacterial countreached about10¹⁰ cfu g^?1 and the pH dropped from6·4 to 3·35 in about 42 h. In this phase, only the latter two species remaineddominant in a ratio of 1:1. From the Sudanese long-term dough, seven strains of Lactobacillus were isolated, representing the dominant flora. Sequence comparison ofpartial 16S rRNA gene sequences were used to clarify their phylogenetic positions. Five strainswere classified as Lact.vaginalis and could be regarded as heterogenous biovars of thisspecies. The other two strains could be assigned to Lact. helveticus .RAPD-PCR and sugar fermentation patterns were useful in differentiation of these strains.