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Directed evolution of a dextransucrase for increased constitutive activity and the synthesis of a highly branched dextran |
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| Authors: | Hee-Kyoung Kang Eun-Seong Seo John F. Robyt Doman Kim |
| Affiliation: | a Engineering Research Institute, Chonnam National University, Gwang-Ju 500-757, South Korea b Faculty of Applied Chemical Engineering and Institute for Catalysis, Chonnam National University, Gwang-Ju 500-757, South Korea c Laboratory of Carbohydrate Chemistry and Enzymology, Iowa State University, Ames, IA 50011, USA |
| Abstract: | An Escherichia coli transformant (pDSRB742CK) was obtained from the DSRB742 clone by using ultrasoft X-rays for the expression of a dextransucrase. The enzyme differed in several aspects from DSRB742 dextransucrase: it (1) was constitutive; (2) was extracellular; (3) had 2.6 times greater activity (0.035 IU/ml and 0.23 IU/mg); and (4) synthesized a highly (15.6%) -(1→3) branched dextran. Seven nucleotides of the parent gene (dsrB742) were changed in the nucleotide sequence; four nucleotides were changed in the open reading frame (ORF) that resulted in a 30 amino acid deletion in the N-terminus. |
| Keywords: | Dextransucrase Directed bacterial evolution Constitutivity Leuconostoc mesenteroides mutants Dextran E. coli dextransucrase transformants |
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