Use of a genetically engineered Escherichia coli strain to produce 1,2- dihydroxy-4'-chlorobiphenyl

Abstract

Genetically engineered kanamycin-resistant Escherichia coli HB101 containing the mutant chimeric plasmid pAW6194-T17 specifying biphenyl dioxygenase and dihydrodiol dehydrogenase and lacking the ability to produce active 3-phenylcatechol dioxygenase was used to produce 1,2-dihydroxy-4'- chlorobiphenyl (DHCB) from 4-chlorobiphenyl. Resting-cell suspensions of genetically engineered E. coli in mineral salts medium (pH 7.0) containing 880 μM 4-chlorobiphenyl produced 110 μM DHCB. The K(m) for 4-chlorobiphenyl was 3.3 mM. Biotransformation of DHCB from 4-chlorobiphenyl was maximum when cells (2.5 mg of protein per ml) were incubated with shaking (150 rpm) at pH 7.0 and 30°C for 6 h. The enzymatically produced DHCB was a suitable substrate for assaying 3-phenylcatechol dioxygenase activity. Biologically produced DHCB showed UV and mass spectra similar to those of chemically synthesized DHCB. The bioconversion rate of ortho-substituted chlorobiphenyl was slower than that of the para- or meta-substituted chlorobiphenyl.