Zygosaccharomyces-Selective Medium

Presumptive identification of a yeast suspected to be Zygosaccharomyces can be made by growing the isolate on media supplemented with 1% acetic acid. Saccharomyces sp. is not able to grow under these conditions. Further, among the species of Zygosaccharomyces, Z. bailli and Z. bisporous grow, whereas Z. rouxii will not. Other native yeast species may also be able to tolerate environmental acetic acid (Boulton et al., 1995). However, as the authors note, refermentation in sorbated sweet wine virtually eliminates these from consideration. 

The selective properties of the following medium rely on incorporation of required volume of acetic acid without volatilization. 

In approximately 700 mL distilled water, dissolve the following 100 g glucose (dextrose) 

With mixing, bring to 1 L volume with distilled water. Sterilize by autoclaving. 

When autoclave cycle is complete, transfer to 45°C (113°F) water-bath and allow temperature to equilibrate. 

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Makdesi, A.K. and L.R. Beughat. 1996. Improved selective medium for enumeration of benzoate-resistant, heat-stressed Zygosaccharomyces bailii. Food Microbiol. 13 281-290. 

Presumptive identification of a yeast suspected to be Zygosaccharomyces can be made by growing the isolate on the Zygosaccharomyces medium supplemented with 1% v/v acetic acid. Whereas Saccharomyces will not grow, most species of Zygosaccharomyces will (Z. bailii and Z. bisporus). Some species, however, will not (Z. rouxii). Other selective media for Zygosaccharomyces dtre available (Makdesi and Beuchat, 1996). 

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