Anti-listerial mixed culture and method for producing cheese

1. A freeze-dried or frozen mixed lactic acid bacterial culture composition comprising:

(a) one or more strains of lactic acid bacteria capable of producing a Class IIa type bacteriocin, wherein at least one of the strains is Lactobacillus spp.; and

(b) one or more strains of lactic acid bacteria capable of producing a Class I type bacteriocin, wherein at least one of the strains of lactic acid bacteria capable of producing a Class I type bacteriocin is selected from the group consisting of Lactococcus spp; and

(c) optionally, one or more further lactic acid bacterial strains; and

(d) one or more additives present in an amount up to 20 wt. % relative to the weight of the composition.

2. The mixed lactic acid bacterial culture composition according to claim 1 , wherein:

(A) at least one or more of the strains of lactic acid bacteria capable of producing a Class IIa type bacteriocin is:

(i) a strain of Lb. plantarum,

(ii) a strain having a 16S rRNA gene with a sequence that has more than 97% similarity with SEQ ID NO 1,

(iii) Lb. plantarum deposited under number LMG P-26358, or

(iv) a mutant of Lb. plantarum (LMG P-26358) which has the capability to produce the same Class IIa type bacteriocin and has 100% 16S rRNA gene similarity with SEQ ID NO 1, and/or wherein at least one or more of the lactic acid bacteria capable of producing a Class I type bacteriocin is a lactic acid bacterial strain which is capable of producing a nisin; or

(B) at least one or more of the lactic acid bacteria capable of producing a Class I type bacteriocin is a lactic acid bacterial strain which is capable of producing a nisin and at least one or more of the strains of lactic acid bacteria capable of producing a Class IIa type bacteriocin is not capable of growing in the presence of the nisin at a concentration of at least 300 IU/mL.

3. The mixed lactic acid bacterial culture composition according to claim 1 , wherein the one or more strains of lactic acid bacteria capable of producing a Class IIa type bacteriocin are present in the composition at a total viable cell count of at least 1×10 8 , and wherein the one or more strains of lactic acid bacteria capable of producing a Class I type bacteriocin are present in the composition at a total viable cell count of at least 1×10 8 .

4. The mixed lactic acid bacterial culture composition according to claim 1 , wherein the one or more strains of lactic acid bacteria capable of producing a Class IIa type bacteriocin comprises the strain of Lb. plantarum deposited under number LMG P-26358, or a mutant thereof which has the capability to produce a Class IIa type bacteriocin and has 100% 16S rRNA gene similarity with LMG P-26358.

5. The mixed lactic acid bacterial culture composition according to claim 1 , wherein the one or more strains of lactic acid bacteria capable of producing a Class I type bacteriocin is selected from L. lactis ssp. lactis biovar. diacetylactis , the strains being capable of producing a nisin.

6. The mixed lactic acid bacterial culture composition according to claim 1 , wherein the composition is in frozen form.

7. The mixed lactic acid bacterial culture composition according to claim 6 , wherein the composition is in the form of frozen particles having a diameter of from about 0.01 mm to about 50 mm.

8. The mixed lactic acid bacterial culture composition according to claim 1 , wherein the additives comprise a cryoprotectant.

9. The mixed lactic acid bacterial culture composition according to claim 1 , wherein the composition consists of:

(1) lactic acid bacteria comprising:

(a) one or more strains of lactic acid bacteria capable of producing a Class IIa type bacteriocin, wherein at least one of the strains is Lactobacillus spp.; and

(b) one or more strains of lactic acid bacteria capable of producing a Class I type bacteriocin, wherein at least one of the strains of lactic acid bacteria capable of producing a Class I type bacteriocin is selected from the group consisting of Lactococcus spp.; and

(c) optionally, one or more further lactic acid bacterial strains

(2) water;

(3) optionally non-lactic acid bacteria.

10. The mixed lactic acid bacterial culture composition according to claim 1 , wherein at least one of the one or more strains of lactic acid bacteria capable of producing a Class IIa type bacteriocin is sensitive towards the Class I bacteriocin(s) produced by the one or more strains capable of producing a Class I type bacteriocin.

11. The mixed lactic acid bacterial culture composition according to claim 10 , wherein the sensitivity sensitive towards the Class I bacteriocin(s) is defined by, when cultured at its optimal growth temperature during 4 h in 10% reconstituted skimmed milk, a growth in the absence of nisin to a colony forming unit density which is at least 5 times higher than the colony forming unit density that is reached when the same strain is incubated in the presence of 320 IU/ml of nisin under otherwise the same conditions.