Construction of Escherichia coli Strains for Conversion of Nitroacetophenones to ortho-Aminophenols
AIR FORCE RESEARCH LAB TYNDALL AFB FL
Pagination or Media Count:
The predominant bacterial pathway for nitrobenzene NB degradation uses an NB nitroreductase and hydroxylaminobenzene HAB mutase to form the ring-fission substrate ortho-aminophenol. We tested the hypothesis that constructed strains might accumulate the aminophenols from nitroacetophenones and other nitroaromatic compounds. We constructed a recombinant plasmid carrying NB nitroreductase nbzA and HAB mutase A habA genes, both from Pseudomonas pseudoalcaligenes JS45, and expressed the enzymes in Escherichia coli JS995. IPTG isopropyl-Beta-D-thiogalactopyranoside-induced cells of strain JS995 rapidly and stoichiometrically converted NB to 2-aminophenol, 2-nitroacetophenone 2NAP to 2-amino-3-hydroxyacetophenone 2AHAP, and 3-nitroacetophenone 3NAP to 3-amino-2-hydroxyacetophenone 3AHAP. We constructed another recombinant plasmid containing the nitroreductase gene nfs1 from Enterobacter cloacae and habA from strain JS45 and expressed the enzymes in E. coli JS996. Strain JS996 converted NB to 2-aminophenol, 2-nitrotoluene to 2-amino-3-methylphenol, 3-nitrotoluene to 2-amino-4-methylphenol, 4-nitrobiphenyl ether to 4-amino-5-phenoxyphenol, and 1-nitronaphthalene to 2-amino-1-naphthol. In larger-scale biotransformations catalyzed by strain JS995, 75 of the 2NAP transformed was converted to 2AHAP, whereas 3AHAP was produced stoichiometrically from 3NAP. The final yields of the aminophenols after extraction and recovery were greater than 64. The biocatalytic synthesis of ortho-aminophenols from nitroacetophenones suggests that strain JS995 may be useful in the biocatalytic production of a variety of substituted ortho-aminophenols from the corresponding nitroaromatic compounds.