Influence of geographical origin and flour type on diversity of lactic acid bacteria in traditional Belgian sourdoughs

Abstract

A culture-based approach was used to investigate the diversity of lactic acid bacteria (LAB) in Belgian traditional sourdoughs and to assess the influence of flour type, bakery environment, geographical origin, and technological characteristics on the taxonomic composition of these LAB communities. For this purpose, a total of 714 LAB from 21 sourdoughs sampled at 11 artisan bakeries throughout Belgium were subjected to a polyphasic identification approach. The microbial composition of the traditional sourdoughs was characterized by bacteriological culture in combination with genotypic identification methods, including repetitive element sequence-based PCR fingerprinting and phenylalanyl-tRNA synthase (pheS) gene sequence analysis. LAB from Belgian sourdoughs belonged to the genera Lactobacillus, Pediococcus, Leuconostoc, Weissella, and Enterococcus, with the heterofermentative species Lactobacillus paralimentarius, Lactobacillus sanfranciscensis, Lactobacillus plantarum, and Lactobacillus pontis as the most frequently isolated taxa. Statistical analysis of the identification data indicated that the microbial composition of the sourdoughs is mainly affected by the bakery environment rather than the flour type (wheat, rye, spelt, or a mixture of these) used. In conclusion, the polyphasic approach, based on rapid genotypic screening and high-resolution, sequence-dependent identification, proved to be a powerful tool for studying the LAB diversity in traditional fermented foods such as sourdough.

FIG. 1.

Biodiversity data were imported into BioNumerics version 4.61 as an open character type, resulting in microbial community profiles reflecting the diversity of dominant LAB species in 21 Belgian traditional sourdoughs analyzed. Descriptive (depositor and type of flour) characteristics are shown; technological characteristics (pH and fermentation time and temperature) are in Table 1. The dendrogram was constructed by using the unweighted-pair group method using arithmetic averages, with correlation levels expressed as percentage-of-similarity values of the Pearson correlation coefficient. Bootstrap values (based on 1,000 replications) at or above 50% are indicated at the branch points.

FIG. 2.

Dendrogram showing the genetic similarities between selected strains of the four most frequently isolated species from Belgian artisan sourdoughs (L. paralimentarius, L. sanfranciscenis, L. plantarum, and L. pontis) based on (GTG)₅-PCR fingerprints. One representative fingerprint pattern per species isolated from sourdough samples originating from depositors D2, D6, D7, D10, and D11 and the pattern of the corresponding type strain (in bold face) were included for cluster analysis. The dendrogram was constructed using the unweighted-pair group method using arithmetic averages, with correlation levels expressed as percentage-of-similarity values of the Pearson correlation coefficient.

FIG. 3.

Three-dimensional score plot of the PCA of the data obtained from 21 Belgian artisan sourdough samples. 1.1, D01WW01T01; 2.1, D02WR01T01; 2.2, D02WR01T02; 2.3, D02WW01T01, 3.1, D03WW01T01; 4.1, D04WW01T01; 5.1, D05WW01T01; 6.1, D01SS01T01; 6.2, D01WW01T01; 7.1, D07WR01T01; 7.2, D07WR01T02; 7.3, D07WR02T01; 8.1, D08WW01T01; 9.1, D09ME01T01; 10.1, D10WW01T01; 10.2, D10SS01T01; 10.3, D10WR01T01; 11.1; D11RR01T01, 11.2, D11WW01T01; 11.3, D11WW02T01; 11.4, D11SS01T01.