EXPRESSION AND SECRETION OF BARLEY ALPHA-AMYLASE AND ASPERGILLUS-NIGER GLUCOAMYLASE IN SACCHAROMYCES-CEREVISIAE

cDNAs of barley a-amylase and A. niger glucoamylase were cloned in one E. coli-yeast shuttle plasmid resulting in the construction of expres sion secretion vector pMAG15. pMAG15 was transformed into S. cerevisia e GRF18 by protoplast transformation. The barley a-amylase and A. nige r glucoamylase were efficiently expressed under the control of promote r and terminator of yeast PGK gene and their own signal sequence. Over 99 % of the enzyme activity expressed was secreted to the medium. The recombinant yeast strain, S. cerevisiae GRF18 (pMAG15), by hydrolyzes 99% of the starch in YPS medium containing 15% starch in 47 h. The gl ucose produced can be used for the production of ethanol.