alpha-Amylase as a marker for evaluating the stability of recombinant yeast in long-term cultivation.

We describe here a simple method for analyzing the stability of recombinant yeast. The mouse salivary alpha-amylase gene was used in this system as a marker since the stability of recombinant yeast can be detected easily by a halo zone-for-ming assay on starch-supplemented plates. We used this method to evaluate the stability of recombinant yeast harbouring a 2 mu directed episomal plasmid and of yeast harbouring the r-DNA directed integrative vector. Our results demonstrated clearly that the alpha-amylase gene was a convenient and reliable marker for evaluating the stability of recombinant yeasts in long-term cultivation.