Selection of yeast hybrids by the sulfonylurea herbicide chlorsulfuron

Summary A new selection method based on the use of chlorsulfuron (CS) resistance as the selection marker for protoplast fusion in industrial yeast has been introduced using the system of protoplast fusion. A petite mutant of a spontaneously CS-resistant distiller's Saccharomyces cerevisiae strain and a wild-type CS-sensitive strain of the osmotolerant yeast Zygosaccharomyces mellis were fused in order to obtain a distiller's yeast suitable for fermentations on concentrated molasses. Fusion products were isolated as large colonies on minimal glycerol agar with 0.5 mg ml^–1 of the herbicide Glean (75% CS). Following prolonged cultivation on molasses, stable hybrid subxlones were obtained. Offprint requests to: F. Cvrková