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KMID : 0545119950050010006
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Journal of Microbiology and Biotechnology
1995 Volume.5 No. 1 p.6 ~ p.13
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Cloning and Expression of Kluyveromyces fragilis β-Galactosidase Gene in Saccharomyces cerevisiae
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BANG, JEONG HEE
NAM, DOO H./KANG, DAE OK/JONG, SEOG AHN/RYU, Dewey D.Y.
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Abstract
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A gene coding for the β-galactosidase (lactase) of Kluyveromyces fragilis UCD 55-55 was isolated by complementation in Escherichia coli YMC9. From the plasmid library made from Sau3A-digested chromosomal DNA, one positive clone was selected. The cloned gene for β-galactosidase was on 7.3 kilobase pair DNA fragment, and a slightly low level of β-galactosidase enzyme activity was detected in E. coli. It was also confirmed that the cloned gene comes from K. fragilis by DNA-DNA hybridization and immunochemical blotting experiments. In order to construct a new yeast strain having the metabolic ability for lactose, the cloned gene for K. fragilis β-galactosidase was inserted in yeast vector YEp24 and YRp17, and transformed into Saccharomyces cerevisiae YNN27 and M1-2B. The yeast transformants showed the nearly the same β-galactosidase productivity as level of K. fragilis when uninduced, but these could not utilize lactose as a sole carbon source, presumably due to the lack of lactose transport system. Nevertheless, a slightly higher ethanol productivity was achieved by these transformants than S. cerevisiae or K. fragilis, in the medium containing glucose and lactose.
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