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