Isolation of antifungally active lactobacilli from Edam cheese

Abstract

The antifungal activity of 322 lactobacilli strains isolated from Edam cheese at different stages of the ripening process was tested against Fusarium proliferatum M 5689 using a dual overlay spot assay. Approximately 21% of the isolates showed a certain level of inhibitory activity.Seven strains with the strongest antifungal activity were examined by the milk agar plate method with three different mould strains isolated from spoiled dairy products as target microorganisms and were compared with the antifungal effectiveness of standard antifungal strains Lactobacillus rhamnosus VT1 and Lb. plantarum DC 1246.The newly isolated lactobacilli strains exhibited the strongest inhibition against F. proliferatum M 5689, followed by Penicillium sp. DMF 0006 and Aspergillus niger DMF 0801. The level of mould growth inhibition of several new isolates, namely Lb. paracasei ST 68, Lb. fermentum ST 40 and Lb. fermentum ST 41, was comparable to or slightly higher than that of standard strains. By use of both phenotypic and genotypic methods (REP-PCR, 16S rDNA), four out of seven antifungally active isolates were identified, one as Lb. paracasei and three as Lb. fermentum. Lb. paracasei ST 68 was chosen for further testing as antifungal protective adjunct for Edam cheese production.