# Functional characterization of thermophilic lactic acid bacteria isolated from Saint-Nectaire cheese PDO area

Anna Grizon, Pascal Bonnarme, Cécile Callon, Eric Dugat-Bony, Sandra Helinck, Christophe Chassard

► To cite this version:

Anna Grizon, Pascal Bonnarme, Cécile Callon, Eric Dugat-Bony, Sandra Helinck, et al. Functional characterization of thermophilic lactic acid bacteria isolated from Saint-Nectaire cheese PDO area. Journée de l'école doctorale SVSAE, Université Clermont-Auvergne, May 2022, Clermont-Ferrand, France. hal-04862890

HAL Id: hal-04862890

https://hal.science/hal-04862890v1

Submitted on 3 Jan 2025

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# FUNCTIONAL CHARACTERIZATION OF THERMOPHILIC LACTIC ACID BACTERIA ISOLATED FROM SAINT-ECTAIRE CHEESE PDO AREA

Anna Grizon¹,², Pascal Bonnarme², Cécile Callon¹, Eric Dugat-Bony², Sandra Helinck², Christophe Chassard¹

¹ Université Clermont Auvergne, INRAE, VetAgro Sup, UMR545 Fromages, 20 côte de Reyne, 15000 Aurillac, France ² Université Paris Saclay, INRAE, AgroParisTech, UMR SayFood, F-78850 Thiverval Grignon, France

## INTRODUCTION

Streptococcus thermophilus and Lactobacillus delbrueckii are among the most important lactic acid bacteria used as starters in the dairy industry. Previous studies have shown that the genetic and functional characteristics of these two species are very homogeneous, which contributes to obtain dairy products with standardized sensorial qualities. However, these studies were carried out on collections of industrial strains that are believed to play similar functional roles. Therefore, the possibility of isolating new wild strains of St. thermophilus and Lb. delbrueckii with high genetic and functional variability from natural habitats has to be investigate. For this reason, we characterized the functional properties of wild strains of St. thermophilus and Lb. delbrueckii isolated from milks of the Saint-Nectaire cheese-producing PDO area (small appelation area of 1800km²). The functional activities of the isolates were characterized according to three main criteria: growth, acidification and proteolysis.

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## MATERIALS AND METHODS

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## RESULTS

### Isolation and identification

<table><caption>Table 1 : number of isolates identified as belonging to the species St. thermophilus and Lb. delbrueckii</caption><thead><tr><td>Isolated species</td><td>Number of isolates</td></tr></thead><tbody><tr><td>St.thermophilus</td><td>58</td></tr><tr><td>Lb.delbrueckii</td><td>50</td></tr></tbody></table>

### Growth kinetics

<table><caption>Table 2 : Generation time of the study isolates</caption><thead><tr><td>Isolated species</td><td>Generation time</td></tr></thead><tbody><tr><td>St.thermophilus</td><td>1h 50min ≤ G ≤ 2h 50min</td></tr><tr><td>Lb.delbrueckii</td><td>3h ≤ G ≤ 4h 15min</td></tr></tbody></table>

### Acidification kinetics

<figure><img src="image_4.png" /><figcaption>Figure 1 : Acidification kinetics of four isolates representative of the four identified acidification categories</figcaption></figure>

<table><caption>Table 3 : Number of isolates belonging to the different acidification categories</caption><thead><tr><th>Categories</th><th>Isolates<br>St.thermophilus</th><th>Isolates<br>Lb.delbrueckii</th></tr></thead><tbody><tr><td>1</td><td>25</td><td>50</td></tr><tr><td>2</td><td>11</td><td>0</td></tr><tr><td>3</td><td>15</td><td>0</td></tr><tr><td>4</td><td>7</td><td>0</td></tr></tbody></table>

### Proteolytic activities

<figure><img src="image_5.png" /><figcaption>Figure 2 : Proteolytic activities of nine isolates representative of the three identified proteolysis categories</figcaption></figure>

<table><caption>Table 4 : Number of isolates belonging to the different proteolysis categories</caption><thead><tr><th>Categories</th><th>Isolates<br>St.thermophilus</th><th>Isolates<br>Lb.delbrueckii</th></tr></thead><tbody><tr><td>1</td><td>58</td><td>19</td></tr><tr><td>2</td><td>0</td><td>25</td></tr><tr><td>3</td><td>0</td><td>6</td></tr></tbody></table>

## CONCLUSION AND PROSPECTS

The collection of *St. thermophilus* and *Lb. delbrueckii* strains isolated from raw milks of the AOP Saint-Nectaire cheese production area exhibited **heterogeneous functional characteristics**. **St. thermophilus** isolates showed various **acidifying activities**, but little diversity of proteolytic activities. In contrast **Lb. delbrueckii** isolates are characterized by a significant **diversity of proteolytic activities**, but a limited range of acidifying activity. However, the intra-species growth kinetics of isolates did not vary significantly. Identification of the aromatic compounds produced by these isolates (GC-MS), as well as the analysis of complete genomes of isolates will be carried out in order to implement the data presented in this work and study the genetic and functional diversity of wild strains of *St. thermophilus* and *Lb. delbrueckii* isolated from the Saint-Nectaire PDO area