Impact of Lachancea thermotolerans inoculation on microbial diversity during Spanish-style green table olive fermentations

Table olives are among the most widely consumed fermented vegetable products worldwide, with production largely concentrated in Mediterranean countries such as Spain, Italy, and Greece. Despite their economic importance, the industry continues to face technological challenges, particularly the poor initial survival and implantation of commercial starter cultures. This limitation has driven increasing interest in the exploration of alternative microorganisms with enhanced adaptability and biotechnological potential.

In this study, the effect of selected Lachancea thermotolerans strains was evaluated in Spanish-style green table olive fermentations, followed by sequential inoculation with Lactiplantibacillus plantarum. Fermentation dynamics were monitored through physicochemical and microbiological analyses. In addition, a metagenomic approach was applied to characterize microbial community evolution and to assess the possible impact of L. thermotolerans inoculation. Sensory evaluation of the final products was also performed.

Metagenomic results revealed a remarkable and sustained persistence of L. thermotolerans throughout the fermentation process, with detectable abundance maintained for over 90 days. Furthermore, fermentations inoculated with the L. thermotolerans– L. plantarum consortium showed accelerated acidification kinetics, promoting the rapid establishment and dominance of lactic acid bacteria, while improving organoleptic profiles and sensory scores compared to controls.

Overall, the studied L. thermotolerans strains demonstrate significant potential as robust starter cultures for table olive fermentation, particularly due to their exceptional persistence as evidenced by metagenomic analysis. These findings support their application as a strategy to improve fermentation reliability and product quality. Further studies at industrial scale are warranted to confirm their performance under commercial conditions.

Acknowledgements: Project PID2021-125864OA-I00 funded by MCIN/AEI/10.13039/ 501100011033/ and FEDER. Besides, David Penco-Parra and Patricia Gil-Flores thank for their research contracts PCI IN000616 and IN00028609 funded by MCIN and FEDER, respectively.