초록
<P><B>Abstract</B></P><P><B>BACKGROUND: The effects of pretreated beet molasses based feeding strategies on thermostable glucose isomerase (GI) production by recombinant <I>Escherichia coli</I> BL21 (DE3) pLysS were investigated.</B></P><P><B>RESULTS: The thermostable GI encoding gene of <I>Thermus thermophilus</I> (<I>xyl</I><SUB><I>A</I></SUB>) was recombined with pRSETA vector, and the pRSETA::<I>xyl</I><SUB><I>A</I></SUB> obtained was transferred into <I>E.coli</I> BL21 (DE3) pLysS and used for GI production. The highest soluble GI activity was obtained at <I>t</I> = 30 h, as A = 16 400 U L<SUP>−1</SUP> (20.6 U mg<SUP>−1</SUP> protein) under molasses based fed‐batch operation, with a specific growth rate µ = 0.1 h<SUP>−1</SUP> (M‐0.1); on the other hand, the highest cell concentration was obtained at µ = 0.15 h<SUP>−1</SUP> operation as 9.6 g L<SUP>−1</SUP> at <I>t</I> = 32 h. The highest oxygen uptake was 4.57 mol m<SUP>−3</SUP> s<SUP>−1</SUP> at M‐0.1 operation.</B></P><P><B>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 <I>E. coli</I> strains. © 2012 Society of Chemical Industry</B></P>