Hafnia alvei B16, the anti-STEC solution from Lallemand
The contamination of milk and cheese by Shiga toxin-producing Escherichia coli (STEC) represents a major concern for the cheese industry, particularly for the cheesemakers of raw milk cheeses.
Some technologies such as those which produce soft cheese, uncooked pressed cheese (particularly those with a short ripening step) and blue-veined cheese are more prone to STEC contamination. Lactic and hard cheeses, on the other hand might potentially be protected based on their lower pH and cooking step. (1)
The prevention of STEC contamination is best done upstream in the cheese manufacturing by following strict hygiene rules specifically during breeding, milking and processing.
For its first newsletter, Lallemand Specialty Cultures would like to share the latest development in its biopreservation strategy: a culture that has demonstrated capacity to inhibit STEC growth in different cheese matrices.
The project BLASTEC(2) was initiated in partnership between INRA, Aurillac (Cécile Callon and Marie Christine Montel)(3), LALLEMAND(4) and others to identify a novel and promising anti-STEC solution. The capacity to inhibit STEC growth of 149 microorganisms from milk origin was tested in model systems including experimental cheese manufacturing.
The table and graph below show the STEC inhibition of the 6 most efficacious strains in curd and uncooked pressed cheese model systems. As observed, the Hafnia alvei B16 strain proved to be the most efficacious against the 3 STEC serotypes tested in this study.
STEC inhibition capacity (logarithmic decrease) of several strains tested during the project Blastec (5).
Inoculation level of the inhibiting strain : 106 CFU/ml of milk.
STEC inoculation level : 102 CFU/ml of milk.
These STEC inhibition capacities were demonstrated several times in uncooked pressed cheese (St Nectaire, Cantal) and blue-veined cheese by INRA, Aurillac. The study also demonstrated a mild aromatic contribution from Hafnia alvei B16(6).
The mechanisms involved in STEC inhibition by Hafnia alvei B16 are still to be understood. It does not result from a pH decrease as the inhibition effect remains the same even in strongly buffered medium. The Hafnia alvei B16 strain produces levels of hydrogen peroxide that are too low to explain the behavior; neither does it possess the aat and abt genes responsible for the alveicin, the bacteriocin produced by other Hafnia alveistrains(6).
The partnership with INRA is continuing in 2017 in order to understand the mechanisms involved in STEC inhibition and to develop the second generation of anti-STEC solution.
Lallemand has acquired from INRA the exclusive license to produce Hafnia alvei B16. The strain in frozen pellet form is currently being tested by several industrial cheesemakers.
For further information about Lallemand’s anti-STEC solutions, please contact your local LSC sales representative.
(1) Miszczycha et al. 2012. Behavior of different Shiga Toxin-Producing Escherichia coli Serotypes in Various Experimentally Contaminated Raw-Milk Cheeses.
Applied and Environmental Microbiology 79: 150-158
(2) Projet Blastec funded by FUI-FEDER, N° AAP : 1010011M 10. Raw milk biopreservation against Shiga toxin-producing Escherichia coli.
(3) INRA Aurillac : UFR-INRA UR545 : 20 Côte de Reyne, 15000 Aurillac.
(4) LALLEMAND SAS : 19 rue des Briquetiers, BP59, 31702 Blagnac cedex
(5) Callon et al. 2016. Control of Shigatoxin-producing Escherichia coli in cheese by dairy bacterial strains.
Food Microbiology 53 (2016) 63-70
(6) Project Blastec activity reports