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This study delved into the evolution of fungal population during the fermentation of Spanish-style green table olives (Manzanilla cultivar), determining the influence of different factors such as fermentation matrix (brine or fruit) or the use of a lactic acid bacteria inoculum, on its distribution. The samples (n = 24) were directly obtained from industrial fermentation vessels with approximately 10.000 kg of fruits and 6.000 L of brines. Our findings showcased a synchronized uptick in lactic acid bacteria counts alongside fungi proliferation. Metataxonomic analysis of the Internal Transcribed Spacer (ITS) region unearthed noteworthy disparities across different fermentation time points (0, 24, and 83 days). Statistical analysis pinpointed two Amplicon Sequence Variants (ASV), Candida and Aureobasidium, as accountable for the observed variances among the different fermentation time samples. Notably, Candida exhibited a marked increase during 83 days of fermentation, opposite to Aureobasidium, which demonstrated a decline. Fungal biodiversity was slightly higher in brines than in fruits, whilst no effect of inoculation was noticed. At the onset of fermentation, prominently detected genera were also Mycosphaerella (19.82 %) and Apohysomyces (16.31 %), hitherto unreported in the context of table olive processing. However, their prevalence dwindled to nearly negligible levels from 24th day fermentation onwards (<2 %). On the contrary, they were replaced by the fermentative yeasts Saccharomyces and Isstachenkia. Results obtained in this work will be useful for designing new strategies for better control of table olive fermentations., Competing Interests: Declaration of competing interest The authors declare that there is no conflict of interest regarding the publication of this article., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Lactiplantibacillus pentosus (Lbp. pentosus) is a species of lactic acid bacteria with a great relevance during the table olive fermentation process, with ability to form non-pathogenic biofilms on olive epidermis. The objective of this work is to deepen into the genetic mechanisms of adaptation of Lpb. pentosus LPG1 during Spanish-style green table olive fermentations, as well as to obtain a better understanding of the mechanisms of adherence of this species to the fruit surface. For this purpose, we have carried out a transcriptomic analysis of the differential gene expression of this bacterium during 60 days of fermentation in both brine and biofilms ecosystems. In brines, it was noticed that a total of 235 genes from Lpb. pentosus LPG1 were differentially expressed during course of fermentation and grouped into 9 clusters according to time-course analysis. Transport and metabolism of carbohydrates and amino acids, energy production, lactic acid and exopolysaccharide synthesis genes increased their expression in the planktonic cells during course of fermentation. On the other hand, expression of genes associated to stress response, bacteriocin synthesis and membrane protein decreased. A total of 127 genes showed significant differential expression between Lpb. pentosus LPG1 planktonic (brine) and sessile (biofilms) cells at the end of fermentation process (60 days). Among the 64 upregulated genes in biofilms, we found genes involved in adhesion (strA), exopolysaccharide production (ywqD, ywqE, and wbnH), cell shape and elongation (MreB), and well as prophage excision. Deeping into the genetic bases of beneficial biofilm formation by Lpb. pentosus strains with probiotic potential will help to turn this fermented vegetable into a carrier of beneficial microorganisms to the final consumers. [ABSTRACT FROM AUTHOR]

This work evaluates the effect of 1-methylcyclopropene (1-MCP) on postharvest and fermentation of Manzanilla cultivar, processed as Spanish-style or directly brined table olives. During postharvest handling, 1-MCP (2.85 µL/L) reduced the number of colour-turning olives by 18.42% over the untreated fruits. In Spanish-style and directly brined fermentation, the 1-MCP treatment led to lower pH levels, higher titratable acidities, improved firmness and colour olives than untreated fruits. A panel of expert testers also gave higher scores, and overall acceptability to the 1-MCP treated fruits, especially in the case of Spanish-style fermented olives. Metagenomic analysis of olive biofilms at the end of the fermentation process (176 days) revealed that Lactiplantibacillus was the most abundant bacterial genus in both Spanish-style and directly brined olives (>72%). However, fungal biodiversity was higher than bacterial in all treatments. Saccharomyces was the predominant yeast genus associated with directly brined olives (>97%), whilst Wickerhamomyces (>37%) and Zygoascus (>18%) were with Spanish-style fermentations. The 1-MCP treatment doubled the presence of Wickerhamomyces in Spanish-style fruits (74%) whilst reducing the presence of Zygoascus and allowing the growth of Enterobacter (15%) in directly brined olives. Thus, the postharvesting treatment of table olives with 1-MCP could help reduce the maturation progress of olives and improve the organoleptic and quality characteristics of the products without affecting the microbiological evolution of the fermentations. [ABSTRACT FROM AUTHOR]

In this work, metataxonomic-compositional data analysis was applied to study the influence of inoculation, type of ecosystem (brine or fruit), and time of fermentation (0, 24, and 83 days) on the bacterial composition dynamic during industrial Manzanilla Spanish-style green table olive fermentations. Differences in the physicochemical and microbiological characteristics between inoculated and spontaneous fermentations were scarce, except for the high lactic acid bacteria population (>10 million CFU/g) in the inoculated olive biofilms. The metataxonomic analysis showed eight relevant taxa (Lactiplantibacillus, Vibrio, Halolactibacillus, Aerococcus, Catenococcus, Salinivibrio, Alkalibacterium, and Marinilactibacillus) and absence of pathogens, but the microbiota composition markedly changed throughout fermentation. At the process onset, the main genera were Vibrio, Halolactibacillus, Marinilactibacillus, and Alkalibacterium, while Lactiplantibacillus was almost absent. Regardless of inoculation, Lactiplantibacillus became the predominant genus as the fermentation progressed, albeit Vibrio, Marinilactibacillus, Alkalibacterium, and Halolactibacillus also persisted until the end of the process (but did not cause spoilage). Ferrimonas genus was detected for the first time in table olives, being found in 71% of the samples. Besides, there was more bacterial biodiversity in the brine ecosystem than olive biofilms. Overall, inoculation led to more homogenous and equilibrated bacterial populations at the end of the process. This study expands the knowledge on the bacterial population changes occurring during industrial table olive fermentation, the differences between populations in brines and biofilms, and the beneficial effects of inoculation for using table olives as a carrier of beneficial microorganisms. • Compositional analysis provided new insights of food metataxonomic data. • Low number of bacterial genera typifies green Spanish-style table olive processing. • Lactiplantibacillus became the predominant genera as the fermentation progressed. • Inoculation led to more homogenous bacterial populations at the end of the process. [ABSTRACT FROM AUTHOR]