Effect of Dyes on the Growth of Food Yeasts

Organic dyes were incorporated in YM medium individually at various concentrations (1:1,000 to 1:1,000,000 dilutions) to test their effects on growth of 33 food-related yeasts (e.g. Saccharomyces spp. and Candida spp.). Of 101 dyes tested, many (e.g. Bismarck brown Y, Brilliant cresyl blue, Congo red, Crystal violet, Diphenyl red 4BS supra, Erionyl Red B, Jannus green B, Malachite green, Methyl green, Methyl red, Methyl violet 2B, Nylomine red C-G, Phenosafranin, Safranin Y, Telon yellow GRL) showed potential application for selective isolation and differentiation of specific food yeast species. Candida lipolytica can be effectively selected from other yeasts on a Crystal violet medium (1: 1,000) and Malachite green medium (1:250,000) by providing distinctive white coarsely folded colonies. Trypan blue, Atlantic sky blue FF, Erie brilliant violet B, Eriosin blue B, and Jenner's stain contributed their characteristic violet or blue to the colonies, which may help counting or differentiation on primary plating agar.