GENETIC-ENGINEERING OF BAKERS AND WINE YEASTS USING FORMALDEHYDE HYPERRESISTANCE-MEDIATING PLASMIDS

Yeast multi-copy vectors carrying the formaldehyde-resistance marker g eneSFA have proved to be a valuable tool for research on industrially used strains of Saccharomyces cerevisiae. The genetics of these strain s is often poorly understood, and for various reasons it is not possib le to simply subject these strains to protocols of genetic engineering that have been established for laboratory strains of S. cerevisiae. W e tested our vectors and protocols using 10 randomly picked baker's an d wine yeasts all of which could be transformed by a simple protocol w ith vectors conferring hyperresistance to formaldehyde. The applicatio n of formaldehyde as a selecting agent also offers the advantage of it s biodegradation to CO2 during fermentation, i.e., the selecting agent will be consumed and therefore its removal during down-stream process ing is not necessary. Thus, this vector provides an expression system which is simple to apply and inexpensive to use.