Fermentative degradation of triethanolamine by a homoacetogenic bacterium

Abstract

With triethanolamine as sole source of energy and organic carbon, a strictly anaerobic, gram-positive, rod-shaped bacterium, strain LuTria 3, was isolated from sewage sludge and was assigned to the genus Acetobacterium on the basis of morphological and physiological properties. The G + C content of the DNA was 34.9 + 1.0 mol %. The new isolate fermented triethanolamine to acetate and ammonia. In cell-free extracts, a triethanolaminedegrading enzyme activity was detected that formed acetaldehyde as reaction product. Triethanolamine cleavage was stimulated 30-fold by added adenosylcobalamin (coenzyme B12) and inhibited by cyanocobalamin or hydroxocobalamin. Ethanolamine ammonia lyase, cetaldehyde:acceptor oxidoreductase, phosphate acetyltransferase, acetate kinase, and carbon monoxide dehydrogenase were measured in cell-free extracts of this strain. Our results establish that triethanolamine is degraded by a orrinoid-dependent shifting of the terminal hydroxyl group to the subterminal carbon atom, analogous to a diol dehydratase reaction, to form an unstable intermediate that releases acetaldehyde. No anaerobic degradation of triethylamine was observed in similar enrichment assays.