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To express constitutively the inulinase gene (INU1) of Kluyveromyces marxianus in Sacgaromyces cervisiae, three yeast promoters such as GAPDH, ADH1 and ENO1 were connected upstream of INU1. The resulting plasmids, pYIGP, pADH1-INU, and pENO-INU were introduced to S. cerevisiae SEY2102 host strain, resperctively, and then each transformats were selected by staining of colonies on sucrose-agar plate. When the yeast transformants were cultivated on 2% dextrose media, the total expression levels of inulinase reached to 1.11 unit/mL, 0.88 unit/mL, and 0.69 unit/mL for respective GAPDH, ADH1, and ENO1 promoter systems. On 4% dextrose media, however, the inulinase activities were observed at 2.00 unit/mL for pYIGP, 0.71 unit/mL for pADH1-INU, and 1.40 unit/mL for pENO-INU. This result indicates that the constitutive espression of INU1 was significantly affected by the initial concentration of dextrose and the promoter strength was in the order GAPDH, ENO1 promoter at high dextrose conccntration. Tdking into account the plasmid stability, however, it is suggested that the ENO1 promoter system is more suitable for the INU1 expression on high dextrose medium or in the fed-bath cultivation accumultig ethanol at high level.
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