A differential medium for the isolation of Kluyveromyces marxianus and Kluyveromyces lactis from dairy products

A selective and differential solid medium, called Kluyveromyces Differentia l Medium (KDM), is described for the isolation of Kluyveromyces marxianus a nd K. lactis from dairy products. Its discriminative potential. is based on the detection of the enzyme beta-galactosidase, in the absence of lactose. Of the more than 95 strains tested, including yeasts, bacteria, and filame ntous fungus, only the strains of K. marxianus and K. lactis produced blue colonies on the medium due to the presence of X-Gal/IPTG. The bacterial str ains were not able to grow in KDM. On this basis, the medium was very satis factory when testing naturally or experimentally contaminated dairy food pr oducts. When quality assessment tests were performed, optimal values of pro ductivity (growth and color) and selectivity were obtained for K. marxianus and K. lactis.