Culture-independent detection of microorganisms in traditional Slovakian bryndza cheese

Abstract

In order to investigate the microflora of Slovakian bryndza cheese (a cheese containing unpasteurized or pasteurized ewes' milk component) by a culture-independent method, DNA was extracted directly from 7 bryndza samples and analysed by an innovative method. Using the universal prokaryotic and fungal primers, ribosomal DNA internal transcribed spacer (ITS) regions with variable length were amplified. The standard universal reverse primer L1 aligning to bacterial 23s rDNA was found unsuitable for some lactic acid bacteria and other species based on in silico analysis. Therefore, L1 primer was replaced by a combination of novel primers GplusR and GminusR aligning to the adjacent, more conserved DNA region. The amplification profiles were visualised by both standard electrophoresis and by fluorescent capillary gel electrophoresis. From representative samples, major amplicons were excised from the gel, cloned and sequenced. Sequencing revealed that the samples contained Lactobacillus delbrueckii, Lactobacillus brevis, Streptococcus thermophilus, Lactococcus lactis, Lactococcus raffinolactis, Streptococcus macedonicus, Leuconostoc pseudomesenteroides, Debaromyces hansenii, Mucor fragilis, Yarrowia lipolytica and Galactomyces geotrichum. These results represent an extension of the knowledge on the microflora of Slovakian bryndza cheese. The introduced automated ribosomal DNA intergenic spacer analysis of the bacterial and fungal genomes proved to be very effective in the application of studying microflora of cheese.