Polyphasic Characterisation of Microbiota Associated with Sant'Agostino Table Olives Flavoured with Foeniculum vulgare

Abstract

Sant’Agostino green table olives, traditionally processed in Apulia and flavoured with Foeniculum vulgare, represent a niche product whose microbial ecology remains largely unexplored. This study aimed to characterise the microbiota of the final product (both brine and fruit) after six months of storage with wild fennel. Four production batches were analysed using a combined culture-dependent and culture-independent approach. Microbiological counts revealed variable levels of aerobic mesophilic microorganisms, yeasts, lactic acid bacteria (LAB), and staphylococci, with yeasts and LAB being predominant. Ten LAB strains were identified, including Enterococcus faecium, Leuconostoc mesenteroides subsp. jonggajibkimchii, Leuconostoc mesenteroides subsp. cremoris, Leuconostoc pseudomesenteroides, Lactiplantibacillus plantarum, and Lactiplantibacillus pentosus. Yeast isolates belonged to Candida tropicalis, Torulaspora delbrueckii, and Saccharomyces cerevisiae. Amplicon sequencing (MiSeq Illumina) revealed distinct bacterial profiles between fruit and brine samples, with taxa from Actinobacteria, Bacteroidetes, Enterococcus, Lactobacillus, Leuconostoc, Alphaproteobacteria, Enterobacteriaceae, and other Gammaproteobacteria. Enterococcus and Leuconostoc were consistently detected, while Lactobacillus sensu lato appeared only in one fruit and one brine sample. These findings provide new insights into the microbial diversity of Sant’Agostino olives and contribute to the understanding of their fermentation ecology and potential for quality and safety enhancement.