Assessment of the bacterial community in directly brined Aloreña de Málaga table olive fermentations by metagenetic analysis

Abstract

This study uses an "omics" approach to evaluate the bacterial biodiversity changes during fermentation process of natural green cracked Aloreña de Málaga table olives, from raw material to fermented fruit. For this purpose, two industries separated by almost 20km in Guadalhorce Valley (Málaga, Spain) were analysed for obtaining both brines and fruit samples at different moments of fermentation (0, 7, 30 and 120days). Physicochemical and microbial counts during fermentation showed the typical evolution of this type of processes, apparently dominated by yeasts. However, high-throughput barcoded pyrosequencing analysis of V2-V3 hypervariable region of the bacterial 16S rRNA gene showed at 97% identity the presence of 131 bacterial genera included in 357 operational taxonomic units, not detected by the conventional approach. The bacterial biodiversity was clearly higher in the olives at the moment of reception in the industry and during the first days of fermentation, while decreased considerably as elapse the fermentation process. The presence of Enterobacteriaceae and Lactobacillaceae species was scarce during the four months of study. On the contrary, the most important genus at the end of fermentation was Celerinatantimonas in both brine (95.3% of frequency) and fruit (89.4%) samples, while the presence of well-known spoilage microorganisms (Pseudomonas and Propionibacterium) and halophilic bacteria (Modestobacter, Rhodovibrio, Salinibacter) was also common during the course of fermentation. Among the most important bacterial pathogens related to food, only Staphylococcus genus was found at low frequencies (<0.02% of total sequences). Results show the need of this type of studies to enhance our knowledge of the microbiology of table olive fermentations. It is also necessary to determine the role played by these species not previously detected in table olives on the quality and safety of this fermented vegetable.

Microbiological and Physicochemical Changes in Natural Green Heat-Shocked Aloreña de Málaga Table Olives

“…In this work, the microbial populations of the olives which received a heat treatment consisted mainly of Lactobacillus and Pediococcus . In contrast, Medina et al (2016) , using pyrosequencing analysis, reported the presence of undesirable Celerinatantimonas, Pseudomonas , and Propionibacterium as the most abundant genera detected in traditional industrially fermented fruits while the species of the Lactobacillaceae family were in low proportion (3–8%). This work also reveals information about the bacterial biodiversity for CA and FG Aloreña de Málaga denominations, whose alpha-biodiversity indexes and number of OTUs obtained in the present work were considerably higher than in previous studies ( Medina et al, 2016 ).…”

“…Microbial genomic DNA from olive and brine samples at the end of the fermentation process (138 days) was extracted as described by Medina et al (2016) and sent to the Sequencing and Bioinformatic Service of FISABIO (Valencia, Spain) for bacterial metagenomic analysis. 16S rDNA gene amplicons were amplified following the 16S rDNA gene Metagenomic Sequencing Library Preparation Illumina protocol.…”

Bacterial diversity and community structure in Chongqing radish paocai brines revealed using PacBio single‐molecule real‐time sequencing technology

“…Nineteen species of Pseudomonas were identified from this genus in total (Table S2), with most identified as non‐infectious species, except for Pseudomonas oryzihabitans that was detected in sample W2, in a proportion of 0.03%. This genus has previously been shown to be dominant in Korean kimchi, ‘Jiaozi’, brined table olive, Pu‐erh tea, and ‘doubanjiang‐meju’, which is an anaerobic fermentation food derived from broad beans. Li et al .…”

Table Olives More than a Fermented Food

“…Recently, the application of autochthonous strains has arisen to face consumers' demand for more traditional products with a unique sensory profile and peculiar organoleptic properties [60]. Autochthonous strains, being well adapted to the raw material conditions, can easily lead the fermentation process by dominating the table olives microenvironment [3,51].…”