Microbial innovation in table olive fermentation: a decade of research on Lactiplantibacillus pentosus OM13

Abstract

Background. Table olive fermentation is a longstanding biotechnological tradition practice integral to the Mediterranean diet and agri-food sector. Despite its cultural and economic relevance, spontaneous fermentation often suffers from unpredictable microbial dynamics, inconsistent sensory outcomes, and safety concerns due to the presence of spoilage and pathogenic microorganisms. These limitations have generated interest in controlled fermentation strategies based on microbial ecology and starter culture development and application. At the University of Palermo, the food microbiology research group has undertaken a comprehensive programme aimed at improving the quality, safety, and reproducibility of table olive fermentation. Focusing on Sicilian cultivars, particularly Nocellara del Belice, the research group has explored both Spanish-style and Greek-style fermentation methods. This work contributes to a broader scientific effort to understand and manage microbial communities in fermented vegetables, with a special emphasis on the role of lactic acid bacteria (LAB) and yeasts in shaping product quality and safety (10.1016/j.ijfoodmicro.2022.109670). Methods. Central to this research was the application and characterisation of the autochthonous strain Lactiplantibacillus pentosus OM13, was consistently applied across all experimental trials. Originally isolated from Sicilian table olives, OM13 was selected for its robust fermentative capabilities, tolerance to high salinity and phenolic compounds, and ability to dominate the microbial ecosystem during fermentation. Its performance was assessed under various conditions, including different harvesting methods (manual vs. mechanical), irrigation regimes, and fermentation strategies. One of the most innovative approaches was the adaptation of the “pied de cuve” technique, commonly used in winemaking, to table olive fermentation. This involves preparing a small volume of partially fermented brine to inoculate larger batches, promoting early establishment of beneficial microbial populations while reducing the need for large quantities of starter cultures. Additional strategies included OM13 acclimatisation in brine before inoculation, supplementation with nutrients to support microbial growth, and co-inoculation with selected yeast strains (Candida boidinii and Candida norvegica) known for their enzymatic activity and contribution to flavour development. Trials were conducted at both laboratory and industrial scales in collaboration with local producers. Microbial populations were monitored using culture-based methods and molecular profiling such as randomly amplified polymorphic DNA (RAPD)-PCR and 16S rRNA gene sequencing. Physicochemical parameters (pH and salt concentration), volatile organic compounds (VOCs), and sensory attributes were systematically evaluated throughout the fermentation process. Multivariate statistical analyses were used to interpret microbial dynamics and compare fermentation treatments. Results. Across all experiments, Lact. pentosus OM13 consistently dominated the fermentation microbiota, rapidly acidified the brine, and suppressed spoilage organisms including Enterobacteriaceae and Pseudomonads. Molecular analyses confirmed that LAB isolates from inoculated trials closely matched the OM13 genetic profile based on RAPD-PCR and 16S rRNA sequencing. The strain demonstrated strong adaptability to diverse environmental conditions, including high salinity, low pH, and phenolic presence. The “pied de cuve” approach proved particularly effective in promoting native LAB growth while reducing reliance on freeze-dried cultures. This approach preserved microbial diversity and enhanced the expression of cultivar-specific sensory traits. The acclimatisation of OM13 prior to inoculation further improved fermentation performance, accelerating acidification and stabilising microbial communities. Nutrient supple