A beta-glucuronidase-based agar medium for the differential detection of the yeast Debaryomyces hansenii from foods

A selective and differential solid medium, Debaryomyces differential medium (DDM), was used for the isolation of Debaryomyces hansenii. This medium is formulated to allow detection of the beta-glucuronidase enzyme using the chromogenic substrate magenta-glucuro.CHA (5Br-6Cl-3indolyl-beta-D-glucuronide, cyclohexylammonium salt). Of the more than 120 microorganisms tested, including yeasts, bacteria, and a filamentous fungus, only D. hansenii produced violet colonies, thus permitting its easy discrimination from other organisms. When quality assessment tests were performed, optimal productivity and selectivity were obtained for D. hansenii. The medium was also satisfactory when used to test naturally contaminated food products.