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Polyphasic study of the spatial distribution of microorganisms in Mexican pozol, a fermented maize dough, demonstrates the need for cultivation-independent methods to investigate traditional fermentations.

ABSTRACT: 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 genera Leuconostoc 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.

SUBMITTER: Ampe F

PROVIDER: S-EPMC91745 | biostudies-literature | 1999 Dec

REPOSITORIES: biostudies-literature

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Polyphasic study of the spatial distribution of microorganisms in Mexican pozol, a fermented maize dough, demonstrates the need for cultivation-independent methods to investigate traditional fermentations.

Ampe F F ben Omar N N Moizan C C Wacher C C Guyot J P JP

Applied and environmental microbiology 19991201 12

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 f ...[more]

PMID: 10584005

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Project description:The dynamics of the microbial community responsible for the traditional fermentation of maize in the production of Mexican pozol was investigated by using a polyphasic approach combining (i) microbial enumerations with culture media, (ii) denaturing gradient gel electrophoresis (DGGE) fingerprinting of total community DNA with bacterial and eukaryotic primers and sequencing of partial 16S ribosomal DNA (rDNA) genes, (iii) quantification of rRNAs from dominant microbial taxa by using phylogenetic oligonucleotide probes, and (iv) analysis of sugars and fermentation products. A Streptococcus species dominated the fermentation and accounted for between 25 and 75% of the total flora throughout the process. Results also showed that the initial epiphytic aerobic microflora was replaced in the first 2 days by heterofermentative lactic acid bacteria (LAB), including a close relative of Lactobacillus fermentum, producing lactic acid and ethanol; this heterolactic flora was then progressively replaced by homofermentative LAB (mainly close relatives of L. plantarum, L. casei, and L. delbrueckii) which continued acidification of the maize dough. At the same time, a very diverse community of yeasts and fungi developed, mainly at the periphery of the dough. The analysis of the DGGE patterns obtained with bacterial and eukaryotic primers targeting the 16S and 18S rDNA genes clearly demonstrated that there was a major shift in the community structure after 24 h and that high biodiversity-according to the Shannon-Weaver index-was maintained throughout the process. These results proved that a relatively high number of species, at least six to eight, are needed to perform this traditional lactic acid fermentation. The presence of Bifidobacterium, Enterococcus, and enterobacteria suggests a fecal origin of some important pozol microorganisms. Overall, the results obtained with different culture-dependent or -independent techniques clearly confirmed the importance of developing a polyphasic approach to study the ecology of fermented foods.

Project description:Pozol is a traditional prehispanic Mexican beverage made from fermented nixtamal dough; it is still part of everyday life in many communities due to its nutritional properties. It is the product of spontaneous fermentation and has a complex microbiota composed primarily of lactic acid bacteria (LAB). Although this is a beverage that has been used for centuries, the microbial processes that participate in this fermented beverage are not well understood. We fermented corn dough to produce pozol and sampled it at four key times to follow the community and metabolic changes (0, 9 24 and 48 h) by shotgun metagenomic sequencing to determine structural changes in the bacterial community, as well as metabolic genes used for substrate fermentation, nutritional properties and product safety. We found a core of 25 abundant genera throughout the 4 key fermentation times, with the genus Streptococcus being the most prevalent throughout fermentation. We also performed an analysis focused on metagenomic assembled genomes (MAGs) to identify species from the most abundant genera. Genes involving starch, plant cell wall (PCW), fructan and sucrose degradation were found throughout fermentation and in MAGs, indicating the metabolic potential of the pozol microbiota to degrade these carbohydrates. Complete metabolic modules responsible for amino acid and vitamin biosynthesis increased considerably during fermentation, and were also found to be abundant in MAG, highlighting the bacterial contribution to the well-known nutritional properties attributed to pozol. Further, clusters of genes containing CAZymes (CGCs) and essential amino acids and vitamins were found in the reconstructed MAGs for abundant species in pozol. The results of this study contribute to our understanding of the metabolic role of micro-organisms in the transformation of corn to produce this traditional beverage and their contribution to the nutritional impact that pozol has had for centuries in the traditional cuisine of southeast Mexico.

Project description:Throughout Africa, food fermentations are still driven by indigenous microorganisms which influence the nutritional, organoleptic and safety of the final products. However, for improved safety, consistent quality and beneficial health effects, a trend has emerged which involves the isolation of indigenous strains from traditional fermented products to be used as functional starter cultures. These functional starter cultures possess inherent functional characteristics and can contribute to food quality and safety by offering one or more organoleptic, nutritional, technological or health advantage (probiotics). With the aim of selecting potential probiotic starter cultures, Lactobacillus fermentum strains isolated from fermented millet dough were investigated for technological properties and probiotic traits in-vitro.A total of 176?L. fermentum strains were assessed for technological properties including rate of acidification, exopolysaccharide production and amylase activity. Following this, 48 strains showing desirable technological properties were first screened for acid resistance. Sixteen acid resistant strains were assessed for additional probiotic properties including resistance to bile salts, bile salt hydrolysis, antimicrobial property, haemolysis and antibiotics resistance. L. fermentum strains clustered into 3 groups represented by 36 %, 47 % and 17 % as fast, medium and slow acidifiers respectively. About 8 %, 78 % and 14 % of the strains showed strong, weak and no exopolysaccharides production respectively. Amylase activity was generally weak or not detected. After exposure of 48?L. fermentum strains to pH 2.5 for 4 h, 16 strains were considered to be acid resistant. All 16 strains were resistant to bile salt. Four strains demonstrated bile salt hydrolysis. Antimicrobial activity was observed towards Listeria monocytogenes and Staphylococcus aureus but not E. coli and Salmonella enteritidis. Lactobacillus fermentum strains were generally susceptible to antibiotics except 6 strains which showed resistance towards streptomycin, gentamicin and kanamycin.In vitro determination of technological and probiotic properties have shown strain specific difference among L. fermentum strains isolated from fermented millet dough. Sixteen (16) L. fermentum strains have been shown to possess desirable technological and probiotic characteristics in vitro. These strains are therefore good candidates for further studies to elucidate their full potential and possible application as novel probiotic starter cultures.

Dataset Information

Polyphasic study of the spatial distribution of microorganisms in Mexican pozol, a fermented maize dough, demonstrates the need for cultivation-independent methods to investigate traditional fermentations.

Publications

Polyphasic study of the spatial distribution of microorganisms in Mexican pozol, a fermented maize dough, demonstrates the need for cultivation-independent methods to investigate traditional fermentations.

Similar Datasets

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