FIG. 8.

Biotransformation of 7-ethoxycoumarin by a recombinant strain of E. coli expressing the P450RhF gene. (A) Dealkylation of 7-ethoxycoumarin to form 7-hydroxycoumarin. (B) TLC analysis of ethyl acetate extracts from the culture broth of either the expression strain [BL21(DE3)pAG03] (marked with a “+”) or the negative control [BL21(DE3)pET3a] (marked “−”). The time values indicate the number of hours following inoculation. Substrate (0.5 mM) was added to the medium at the time of inoculation. Different concentrations of 7-hydroxycoumarin were prepared in the culture medium and then extracted into ethyl acetate to act as standards. These were normalized to allow estimation of the percentage of conversion of substrate to product. The concentration (mM) of each standard was as follows: A, blank; B, 0.01; C, 0.05; D, 0.10; E, 0.25; F, 0.50; and G, 1.00.