FIG. 7.

Proposed pattern of enzyme-catalyzed reactions during biotransformation of m-nitrotoluene by E. coli JM101(pSPZ3). Vertical direction: XMO catalyzed the multistep oxygenation of m-nitrotoluene to the corresponding alcohol (a), aldehyde (b), and acid (c). m-Nitrobenzaldehyde formation was counteracted by alcohol dehydrogenase activities of the enzymatic background of the E. coli JM101 host, which reduced it to the corresponding alcohol (d). Additionally, in P. putida DOT-T1E and P. putida PpS81, m-nitrobenzaldehyde was oxidized to the corresponding acid (e). Horizontal direction: all tested bacterial strains reduced nitroaromatics to aromatic amines (f to i), which strongly inhibited XMO-catalyzed oxidation. The formation of unstable m-aminobenzaldehyde by nitroreductases (h) remains unclear.