Strains and media
Escherichia coli Trans1-T1 (Transgene) was used as host for cloning, plasmid propagation and library construction. Escherichia coli BL21(DE3) was used as host for library screening and validation. Bacteria were generally cultured on Luria–Bertani (LB) liquid medium (10 g/L Tryptone, 5 g/L Yeast extract, 10 g/L NaCl, PH adjusted to 7.0) , incubated at 37 °C.
When required, media were supplemented with chemical substrates, and the working concentrations of which were as follows: ampicillin (100 mg/l), chloramphenicol (35 mg/l), anhydrotetracycline (30 mg/l), L-arabinose(10 mM).