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1791657 
Journal Article 
Beet molasses based exponential feeding strategy for thermostable glucose isomerase production by recombinant Escherichia coli BL21 (DE3) 
Angardi, V; Calik, P 
2013 
1 
Journal of Chemical Technology and Biotechnology
ISSN: 0142-0356 
88 
5 
845-852 
WOS:000317674400014 
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 L1 (20.6 U mg1 protein) under molasses based
fed-batch operation, with a specific growth rate mu = 0.1 h1 (M-0.1); on the other hand, the
highest cell concentration was obtained at mu = 0.15 h1 operation as 9.6 g L1 at t = 32 h. The
highest oxygen uptake was 4.57 mol m3 s1 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. (c) 2012 Society of Chemical Industry 
exponential feeding; oxygen transfer; glucose isomerase; molasses; E; coli; T7 promoter