Delving into the study of lactic acid bacteria and yeasts distribution in table olive biofilms using a non-destructive procedure

To turn table olives into appropriate carriers of beneficial bacteria and yeasts to consumers, it is essential to have reliable methods for analysing microorganisms in biofilms. This work validates the application of a non-destructive procedure to study the lactic acid bacteria and yeasts distribution in fruits during Spanish-style green table olive fermentations. Laboratory-scale fermentations were inoculated simultaneously with three Lactiplantibacillus pentosus strains (LPG1, 119, and 13B4) and two yeasts (Wickerhamomyces anomalus Y12 and Saccharomyces cerevisiae Y30), all of them natives of table olive fermentations. Data showed that L. pentosus LPG1 and yeasts W. anomalus Y12 were quite prone to colonise olive biofilms, but only the Lactiplantibacillus strain also can penetrate the epidermis of the fruit and colonise the flesh. Applying a non-destructive treatment consisting in shelling the fruits with glass beads led to obtaining similar lactic acid bacteria and yeast recovery than the classical stomacher destructive method. However, the glass bead procedure improved the quality of the meta-genomics analysis (especially when using 16 S rRNA gene-based sequencing). Results show the great utility of procedures that do not destroy the fruit for studying fermented vegetable biofilms.

Automated summary

In order to transform table olives into carriers of beneficial bacteria and yeasts, it is necessary to develop reliable methods for analyzing microorganisms in biofilms. This study validates the use of a non-destructive procedure to study the distribution of lactic acid bacteria and yeasts in fruits during Spanish-style green table olive fermentations. The data shows that L. pentosus LPG1 and yeast W. anomalus Y12 are prone to colonize olive biofilms, with the Lactiplantibacillus strain also penetrating the fruit's epidermis and colonizing the flesh. The non-destructive treatment using glass beads provides similar recovery rates of lactic acid bacteria and yeasts compared to the classical stomacher destructive method, but improves the quality of meta-genomics analysis.