Lactic acid bacteria (LAB) (n ‫؍‬ 152) in African pearl millet slurries and in the metagenomes of amylaceous fermented foods were investigated by screening 33 genes involved in probiotic and nutritional functions. All isolates belonged to six species of the genera Pediococcus and Lactobacillus, and Lactobacillus fermentum was the dominant species. We screened the isolates for the abilities to survive passage through the gastrointestinal tract and to synthesize folate and riboflavin. The isolates were also tested in vitro for their abilities to survive exposure to bile salts and to survive at pH 2. Because the ability to hydrolyze starch confers an ecological advantage on LAB that grow in starchy matrixes as well as improving the nutritional properties of the gruels, we screened for genes involved in starch metabolism. The results showed that genes with the potential ability to survive passage through the gastrointestinal tract were widely distributed among isolates and metagenomes, whereas in vitro tests showed that only a limited set of isolates, mainly those belonging to L. fermentum, could tolerate a low pH. In contrast, the wide distribution of genes associated with bile salt tolerance, in particular bsh, is consistent with the high frequency of tolerance to bile salts observed. Genetic screening revealed a potential for folate and riboflavin synthesis in both isolates and metagenomes, as well as high variability among genes related to starch metabolism. Genetic screening of isolates and metagenomes from fermented foods is thus a promising approach for assessing the functional potential of food microbiotas.In Africa, many amylaceous fermented foods made from cassava and cereals are used as gruels for the complementary feeding of children under five during weaning. In Burkina Faso and Ghana, ben-saalga and koko gruels prepared from fermented pearl millet (Pennisetum glaucum) slurries are frequently consumed by young children (36,62). The microbiota of these fermented foods is dominated by lactic acid bacteria (LAB), which contribute to their nutritional and sanitary qualities (9, 47). We are currently studying pearl millet-based fermented slurries as a model ("ben-saalga model") for investigating the microbiota of this type of cereal-based food with the aim of developing strategies to improve nutritional quality (26,57,62). Many studies have focused on the phenotypic diversity of the LAB that compose the microbiota of tropical fermented foods. However, their functional diversity in isolates and in metagenomes remains to be described.Since niche-specific adaptation has played a central role in the evolution of LAB (41), the building of collections of bacteria from traditional fermented plant foods in tropical countries may enable the identification of a specific gene set that differs from those of LAB isolated from dairy or bakery products. LAB from microbiotas of plant origin that are found in traditional African foods may have probiotic characteristics (3,28,36). These bacteria first have to be selected for ...

The distribution of microorganisms in pozol balls, a fermented maize dough, was investigated by a polyphasic approach in which we used both culture-dependent and culture-independent methods, including microbial enumeration, fermentation product analysis, quantification of microbial taxa with 16S rRNA-targeted oligonucleotide probes, determination of microbial fingerprints by denaturing gradient gel electrophoresis (DGGE), and 16S ribosomal DNA gene sequencing. Our results demonstrate that DGGE fingerprinting and rRNA quantification should allow workers to precisely and rapidly characterize the microbial assemblage in a spontaneous lactic acid fermented food. Lactic acid bacteria (LAB) accounted for 90 to 97% of the total active microflora; no streptococci were isolated, although members of the genus Streptococcus accounted for 25 to 50% of the microflora. Lactobacillus plantarum and Lactobacillus fermentum, together with members of the generaLeuconostoc and Weissella, were the other dominant organisms. The overall activity was more important at the periphery of a ball, where eucaryotes, enterobacteria, and bacterial exopolysacharide producers developed. Our results also showed that the metabolism of heterofermentative LAB was influenced in situ by the distribution of the LAB in the pozol ball, whereas homolactic fermentation was controlled primarily by sugar limitation. We propose that starch is first degraded by amylases from LAB and that the resulting sugars, together with the lactate produced, allow a secondary flora to develop in the presence of oxygen. Our results strongly suggest that cultivation-independent methods should be used to study traditional fermented foods.

Pozol is an acid beverage obtained from the natural fermentation of nixtamal (heat-and alkali-treated maize) dough. The concentration of mono-and disaccharides from maize is reduced during nixtamalization, so that starch is the main carbohydrate available for lactic acid fermentation. In order to provide some basis to understand the role of amylolytic lactic acid bacteria (ALAB) in this fermented food, their diversity and physiological characteristics were determined. Forty amylolytic strains were characterized by phenotypic and molecular taxonomic methods. Four different biotypes were distinguished via ribotyping; Streptococcus bovis strains were found to be predominant. Streptococcus macedonicus, Lactococcus lactis, and Enterococcus sulfureus strains were also identified. S. bovis strain 25124 showed extremely low amylase yield relative to biomass (139 U g [cell dry weight] ؊1 ) and specific rate of amylase production (130.7 U g [cell dry weight] ؊1 h ؊1 ). In contrast, it showed a high specific growth rate (0.94 h ؊1 ) and an efficient energy conversion yield to bacterial cell biomass (0.31 g of biomass g of substrate ؊1 ). These would confer on the strain a competitive advantage and are the possible reasons for its dominance. Transient accumulation of maltooligosaccharides during fermentation could presumably serve as energy sources for nonamylolytic species in pozol fermentation. This would explain the observed diversity and the dominance of nonamylolytic lactic acid bacteria at the end of fermentation. These results are the first step to understanding the importance of ALAB during pozol fermentation.Amylolytic lactic acid bacteria (ALAB) have been reported from different tropical amylaceous fermented foods, prepared mainly from cassava and cereals (e.g., maize and sorghum). Amylolytic strains of Lactobacillus plantarum have been isolated from African cassava-based fermented products (26), and the new ALAB species Lactobacillus manihotivorans (23) was isolated from cassava sour starch fermentations carried out in Colombia. ALAB have also been isolated from cereal-based fermented foods. Olympia et al. (27)

Folate is an essential micronutrient involved in numerous vital biological reactions. The dietary consumption of naturally occurring vitamin B9 is often inadequate in many countries, and supplementation or fortification programs (using synthetic folic acid) are implemented to alleviate folate deficiency. Other food-based alternatives are possible, such as the use of lactic acid bacteria (LAB) to synthesize folate during fermentation. Many studies have been conducted on this topic, and promising results were reported for some fermented dairy products. However, in other studies, folate consumption by LAB or rather low folate production were observed, resulting in fermented foods that may not significantly contribute to the recommended B9 intake. In addition, the optimum conditions for folate biosynthesis by LAB are still not clear. The aim of this review was thus to (i) clarify the ability of LAB to produce folate in food products, (ii) check if the production of folate by LAB in various fermented foods is sufficient to meet human vitamin B9 requirements and (iii) suggest ways to optimize folate production by LAB in fermented food products.