# A New Culture Medium Rich in Phenols Used for Screening Bitter Degrading Strains of Lactic Acid Bacteria to Employ in Table Olive Production

## TL;DR

Researchers developed a new culture medium from olive by-products to identify bacteria that can reduce bitterness in table olives more efficiently than natural fermentation.

## Contribution

A novel Olive Juice Broth medium was created to screen lactic acid bacteria for phenolic compound degradation in olive processing.

## Key findings

- Seven L. plantarum strains showed ≥50% growth and ≥30% phenolic degradation in the Olive Juice Broth.
- Strain B51 reduced debittering time and accelerated the production of hydroxytyrosol and tyrosol compared to spontaneous fermentation.
- The Olive Juice Broth proved effective in selecting bacteria resistant to olive phenolics.

## Abstract

The olive oil industry recently introduced a novel multi-phase decanter with the “Leopard DMF” series, which gives a by-product called pâté, made up of pulp and olive wastewater with a high content of phenolic substances and without pits. This study aims to create a new culture medium, the Olive Juice Broth (OJB), from DMF pâté, and apply it to select bacteria strains able to survive and degrade the bitter substances normally present in the olive fruit. Thirty-five different bacterial strains of Lactiplantibacillus plantarum from the CREA-IT.PE Collection of Microorganisms were tested. Seven strains characterized by ≥50% growth in OJB (B31, B137, B28, B39, B124, B130, and B51) showed a degradation of the total phenolic content of OJB ≥ 30%. From this set, L. plantarum B51 strain was selected as a starter for table olive production vs. spontaneous fermentation. The selected inoculant effectively reduced the debittering time compared to spontaneous fermentation. Hydroxytyrosol, derived from oleuropein and verbascoside degradation, and tyrosol, derived from ligstroside degradation, were produced faster than during spontaneous fermentation. The OJB medium is confirmed to be useful in selecting bacterial strains resistant to the complex phenolic environment of the olive fruit.