*2.2. Bacterial Strains and Recombinant Vectors*

The *E. coli* DJ strain (i.e., strain DH1 *lacA lacZ wcaJ*), as well as plasmid constructions pBBR-glcATPkfiD and pBS-kfoC have previously been used in our laboratory to produce heparosan and chondroitin [13,14]. DNA encoding for UDP-GlcNAc 4-epimerase of *E. coli* K4, KfoA [15] was cloned in Sac1-Sma1 sites of pBAD33 to obtain pBAD-kfoA. Engineered strains constructed in this study are summarized in Supporting information, Table S1.
