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Beet molasses based exponential feeding strategy for thermostable glucose isomerase production by recombinant Escherichia coli BL21 (DE3)

Authors

  • Vahideh Angardi,

    1. Department of Chemical Engineering, Industrial Biotechnology and Metabolic Engineering Laboratory, Middle East Technical University, 06800 Ankara, Turkey
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  • Pınar Çalık

    Corresponding author
    • Department of Chemical Engineering, Industrial Biotechnology and Metabolic Engineering Laboratory, Middle East Technical University, 06800 Ankara, Turkey
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Correspondence to: Pınar Çalık, Department of Chemical Engineering, Middle East Technical University, 06800 Ankara, Turkey. E-mail: pcalik@metu.edu.tr

Abstract

BACKGROUND: The effects of pretreated beet molasses based feeding strategies on thermostable glucose isomerase (GI) production by recombinant Escherichia coli BL21 (DE3) pLysS were investigated.

RESULTS: The thermostable GI encoding gene of Thermus thermophilus (xylA) was recombined with pRSETA vector, and the pRSETA::xylA obtained was transferred into E.coli BL21 (DE3) pLysS and used for GI production. The highest soluble GI activity was obtained at t = 30 h, as A = 16 400 U L−1 (20.6 U mg−1 protein) under molasses based fed-batch operation, with a specific growth rate µ = 0.1 h−1 (M-0.1); on the other hand, the highest cell concentration was obtained at µ = 0.15 h−1 operation as 9.6 g L−1 at t = 32 h. The highest oxygen uptake was 4.57 mol m−3 s−1 at M-0.1 operation.

CONCLUSIONS: Molasses based fed-batch operations were more successful in terms of cell concentration and thermostable enzyme production due to the existence of a natural sugar inducer, galactose, in the molasses composition. This study demonstrates the significance of proper feeding strategy development for over-production of enzymes by recombinant E. coli strains. © 2012 Society of Chemical Industry

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