Assessment of lactobacilli strains as yogurt bioprotective cultures

Eleven antifungal Lactobacillus strains previously isolated from cow and goat milk were fully characterized using molecular and phenotypic methods. Their antifungal activities were tested in milk and yogurt, against fungal species (Debaryomyces hansenii, Kluyveromyces lactis, Kluyveromyces marxianus, Penicillium brevicompactum, Rhodotorula mucilaginosa and Yarrowia lipolytica) commonly involved in the spoilage of dairy products. The antifungal strains belonged to Lactobacillus paracasei, Lactobacillus rhamnosus, Lactobacillus zeae and Lactobacillus harbinensis species and showed different acidifying and growth capacities in milk. All tested Lactobacillus strains showed an antifungal activity in milk with strain-dependent activity spectra. Lb. harbinensis showed a very strong antifungal effect in yogurt by completely inhibiting all tested fungi as compared to control. The other tested strains were much less effective. It is the first time that the antifungal activity of Lb. harbinensis is described. This strain is a potential candidate for yogurt biopreservation.