Efficient utilization of starch by a recombinant strain of Saccharomyces cerevisiae producing glucoamylase and isoamylase

Two plasmids, designated pRT1 and pT1, were constructed to allow the integr ation of a bacterial isoamylase gene (iso) into Saccharomyces cerevisiae G2 3-8 chromosome. The integrative plasmid pRT1 comprises the iso gene from Ps eudomonas amyloderomosa, a portion of S. cerevisiae ribosomal DNA (rDNA), S . cerevisiae trp1 gene deficient in promoter and the bacterial vector pSP72 . The structure of plasmid pT1 is similar to that of pRT1, except that it l acks an rDNA segment. The Aspergillus awamori glucoamylase and P. amylodera mosa isoamylase genes were expressed in the recombinant strain of S. cerevi siae under the control of the yeast alcohol dehydrogenase gene (adh 1)promo ter. southern-blot analysis showed that these plasmids were integrated into the yeast chromosome in tandem repeat and dispersion copies. The recombina nt strains could assimilate starch more efficiently than the recipient stra in with a conversion rate of greater than 95 %.