Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

Identification of the yeasts and bacteria on the surface of Livarot cheese

The microflora on the surface of Livarot cheese from three different dairies at three points during ripening was investigated. A total of 450 bacteria and 450 yeasts were isolated. Bacteria were identified phenotypically using Biotype 100 strips and dereplicated by rep-PCR. Representative strains were identified by BOX or (GTG)5-PCR. Yeast were identified by Fourier Transform-Infrared Spectroscopy.

Physiological and molecular tests were done on representative yeast to confirm their identity. The bacterial flora consisted of 66% of Gram positive and 34 % of Gram negative isolates. The Gram positive bacteria belonged to Brevibacterium sp., Arthrobacter sp., Microbacterium sp., Corynebacterium sp. or Staphylococcus sp. and included the recently described species Brevibacterium aurantiacum, Arthrobacter arilaitensis and Microbacterium gubbeenense. In addition less common genera such as Brachybacterium sp. and Macrococcus sp. and new taxa close to Agrococcus sp. and Leucobacter sp. were also found. The diversity of the Gram negative flora was also high. Eleven different yeast species were found at the surface of the Livarot cheese. Geotrichum candidum dominated the yeast flora. Kluyveromyces lactis appeared only at the beginning of ripening and Yarrowia lipolytica was found later in the ripening.

The dynamics of the dominant bacteria were different in the three cheeses since no spectrum of species was found in common at any time point. The dynamics of the dominant yeasts, at the species level, were simpler. A high degree of microbial diversity was observed on the surface of the Livarot cheese and each dairy had its own individual microbial flora. These results are going to be disseminated by the mean of a scientific paper, which is currently ready for submission. No benefits are expected. End-users of these results are the scientific community in particular dairy microbiologists, but also cheese producers and producers of commercial strains of microorganisms for the smear cheese industry.

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