INDUSTRIAL-SCALE PRODUCTION AND RAPID PURIFICATION OF AN ARCHAEAL BETA-GLYCOSIDASE EXPRESSED IN SACCHAROMYCES-CEREVISIAE

The application of enzymes isolated from extreme thermophiles in biote chnological processes is hampered by their unconventional fermentation conditions. The expression, in mesophilic hosts, of genes encoding fo r thermophilic proteins enables these difficulties to be overcome and permits the production of enzymes in high yield by using conventional fermentation plants and an efficient enzyme purification utilizing hea t precipitation of host proteins. The beta-glycosidase gene from Sulfo lobus solfataricus, a thermoacidophilic archaeon growing at 87 degrees C and pH 3.5, has been cloned and expressed in Saccharomyces cerevisi ae (baker's yeast). The fermentation of a S. cerevisiae strain on a 10 0-litre scale and the two-step purification of the expressed beta-glyc osidase by cell autolysis and extracts thermal precipitation is descri bed. This procedure, after 72 h of autolysis, gave a yield 56-fold hig her with respect to that obtained with the beta-glycosidase from S. so lfataricus.