Fermentation of phenoxyethanol to phenol and acetate by a homoacetogenic bacterium

Abstract

A strictly anaerobic gram-positive, rod-shaped bacterium, strain LuPhetl, was isolated from sewage sludge with phenoxyethanol as sole carbon and energy source, and was assigned to the genus Acetobacterium. The new isolate fermented the alkylaryl ether compound phenoxyethanol stoichiometrically to phenol and acetate, whereas phenoxyacetic acid was not degraded. In cell-free extracts of strain LuPhetl, cleavage of the ether linkage was shown, and acetaldehyde was detected as reaction product. Coenzyme A-dependent acetaldehyde : acceptor oxidoreductase, phosphate acetyltransferase, acetate kinase, and carbon monoxide dehydrogenase were measured in cell-free extracts of this strain. Our results indicate that the ether linkage of phenoxyethanol is cleaved by a shift of the hydroxyl group to the subterminal carbon atom, analogous to a corrinoid-dependent diol dehydratase reaction, to form an unstable hemiacetal that releases phenol and acetaldehyde. Obviously, phenoxyethanol is degraded by the same strategy as in anaerobic degradation of the alkyl ether polyethylene glycol.

Principles of Anaerobic Degradation of Organic Compounds

“…Formation of acetaldehyde as first cleavage product, extreme oxygen sensitivity of the ether-cleaving enzyme in cell-free extracts, and interference with cobalamines strongly suggest that the first step in this degradation is a cobalamine-dependent shift of the terminal hydroxyl group to the subterminal C-atom, analogous to a diol dehydratase reaction (Fig. With these substrates, a terminal free hydroxy substituent can also be shifted to the subterminal carbon atom, releasing acetaldehyde (FRINGS and SCHINK, 1994). This reaction again transforms the ether to a hemiacetal derivative which decomposes easily on its own.…”