PCR-DGGE assessment of the bacterial diversity in Spanish-style green table-olive fermentations

Abstract

The bacterial ecology associated to Spanish-style green olive fermentations has been studied, attending to its dynamics along the time and its distribution, by a culture-independent approach based on PCR-DGGE. Forty-three 10-tonne fermenters were selected from the fermentation yards (patios) of two large table-olive manufacturing companies in southern Spain. The fermenting brines of 20 of these fermenters were previously analyzed through culture-dependent methods, allowing comparisons of both methodologies. A statistical analysis of DGGE banding profiles obtained using bacteria universal primers demonstrated significant evidences of discrimination of bacterial communities by location (patio) and fermentation stage. Specific microbial "fingerprints" could be established for these variables. At least 17 bacterial species were detected, most of them previously isolated from the same fermenters. Most of these species belonged to the lactic acid bacteria (LAB) group. Dominance of species within the Lactobacillus plantarum group was confirmed. Marinilactibacillus sp. and Propionibacterium olivae, which were not isolated in the previous culture-dependent study, were detected. Alkalibacterium sp. and Halolactibacillus sp. were detected for the first time in table olive fermentations. Using Lactobacillus-group specific primers, significant clustering within the DGGE banding profiles was observed, allowing discrimination regarding the actual fermentation stage. These results corroborated the previous culture-dependent study, and added the detection of Alkalibacterium sp. and Pediococcus acidilactici. The species Alkalibacterium sp., Marinilactibacillus sp. and Halolactibacillus sp. are characterized by their ability to carry out lactic acid fermentation under alkaline conditions and thus ascribed within the halophilic and alkaliphilic lactic acid bacteria (HALAB). Their ubiquitous presence suggests that they could play an important role in Spanish-style olive fermentations, especially at the initial fermentation stage. Thus, they could contribute to brine conditioning before L. plantarum group-driven lactic acid fermentation takes place.

Keywords: Biodiversity; HALAB; Lactobacillus plantarum-group; Olive fermentation; PCR-DGGE.