E. coli BL21 (DE3) cells harboring MT genes in the Genes 2016, 7, 106 4 of 13 pET32a (+) vector were grown at 37 ◦C overnight in the presence of 100 mg·L−1 ampicillin. The cultures were then transferred to fresh Lysogeny broth (LB) medium (1%, v/v) and grown to an ...