Dynamics of the microbial community responsible for traditional sour cassava starch fermentation studied by denaturing gradient gel electrophoresis and quantitative rRNA hybridization

The microbial community developing during the spontaneous fermentation of s our cassava starch was investigated by cultivation-independent methods. Den aturing gradient gel electrophoresis (DGGE) of partially amplified 16S rDNA followed by sequencing of the most intense bands showed that the dominant organisms were all lactic acid bacteria (LAB), mainly close relatives of Bi fidobacterium minimum, Lactococcus lactis, Streptococcus sp., Enterococcus saccharolyticus and Lactobacillus plantarum. Close relatives of Lb. panis, Leuconostoc mesenteroides and Ln. citreum were also found. A complementary analysis using hybridization of 16S rRNA with phylogenetic probes was neces sary to detect the presence of the recently discovered species Lb. manihoti vorans. Although it represented up to 13% of the total lactic acid bacteria of sour cassava starch, this species could not be detected by DGGE as the PCR product migrated to the same position as Lc. lactis. In addition, it wa s shown that a strong pH decrease in the time course of fermentation was mo st probably responsible for the competitive selection of acid-resistant LAB vs. both homo and heterofermentative acid-sensitive LAB. (C) 2001 Elsevier Science B.V. All rights reserved.