Reduction of halogenated derivatives of benzoic acid to the corresponding alcohols by Desulfovibrio vulgaris PY1

Desulfovibrio vulgaris strain PY1 was isolated from a 3-chlorobenzoic acid (3CBA) degrading anaerobic enrichment culture, using anaerobic Percoll dens ity centrifugation. When grown on pyruvate (20 mM), in the absence of sulph ate and under strict anaerobic conditions, this organism converted not only the co-substrates benzoate (BA), 3-amino-BA and 3CBA to the corresponding alcohols but also ten other different halogenated benzoic acids, viz., 4-Cl -, 3-Br-, 4-Sr-, 3-I-, 3-F-, 4-F-, 2,4-di-Cl-, 2,5-di-Cl-, 3,4-di-Cl- and 3 ,5-di-Cl-BA. This was verified with HPLC and GC/MS spectrometric analyses. The yields of the co-substrate converted after 30 days of growth were betwe en 20% and 88%, depending on the compounds which had been added at initial concentrations of 500 CIM Sulphate, sulphite, thiosulphate and disulphite i nhibited the formation of 3-Cl-benzyl alcohol (3CBOH), i.e. a 97 to 99% inh ibition, and nitrate and sulphur had no effect (a 7-10% inhibition). In cel l-free extracts, the reduction of 3CBA to 3CBOH required strict anaerobic c onditions, pyruvate or Hz as electron donors and the addition of methylviol ogen (MV), FAD, FMN or ferredoxin as electron carriers. The specific activi ty of the reduction of 3CBA to 3CBOH in crude extract was 5.3 nmol/(mg prot ein min). The reaction was not inhibited by additions of sulphate or sulphi te (5 mM), but was completely inhibited at concentrations of 10 mM 3CBA or 50 mM BA. A carboxylic acid reductase (aldehyde dehydrogenase), which acted on non-activated 3CBA and was responsible for the reduction of 3CBA to 3-C l-benzaldehyde, was found in the soluble fraction (94% of the total activit y). These results demonstrate that strain PY1 was able to effectively reduc e a wide range of halogenated benzoic acids to the corresponding alcohols.