Transformation of a flocculating Saccharomyces cerevisiae using lithium acetate and pYAC4.

A flocculating yeast Saccharomyces cerevisiae ura3 was transformed by the method based on treatment of intact cells with lithium acetate plus single-stranded carrier DNA using the shuttle vector pYAC4. The transformation efficiency was above 10(3) transformants per microgram of plasmid DNA which is similar to other described yeast transformation systems. Under selective pressure, the transformed cells were stable and maintained the flocculation ability. Thus, this simple transformation system can be used for gene expression studies in flocculating yeasts, overcoming disadvantages of conventional methods such as the spheroplast one.