Identification of Saccharomyces cerevisiae in bakery products by PCR amplification of the ITS region of ribosomal DNA

A non-conventional sensitive and specific method for the detection of Sacch aromyces cerevisiae in food is proposed. Polymerase chain reaction (PCR) le d to the identification of this yeast in some commercial bakery products. T he comparative use of two methods of clean-up of DNA from Triticum spp, S c erevisiae and some foods shows an improvement in extraction yield for the p henol-free method. Analysis of some sequences of ribosomal genes shows diff erent amplified products for Triticum and S. cerevisiae. Internal transcrib ed spacer amplification (ITS1/ITS4) produced a single band of about 650 and 800 bp for Triticum and S. cerevisiae, respectively. ITS1/ITS2 universal f ungal primers gave a single band of about 300 and 450 bp for Triticum and S . cerevisiae, respectively. Both amplification products are able to disting uish between the yeast and the DNA from T. aestivum and T. durum, showing p olymorphism in the ITS1 region. Amplification on two primers designed using the sequence of the ITS1 region of S. cerevisiae rDNA (SC1/SC2) led to a s ingle band of 300 bp, species-specific for the yeast. These primers enabled an unambiguous distinction between fermented foods containing S. cerevisia e and those leavened by baking powders to be made. We suggest that this PCR assay could be used for quality control and for the trace detection of S. cerevisiae as a potential food allergen.