EFFECTS OF TRACE-METAL IONS ON THE GROWTH, HOMOACETOGENESIS AND CORRINOID PRODUCTION BY CLOSTRIDIUM-THERMOACETICUM

The influence of metal ions such as Fe2+, Se4+, Mo6+, and Co2+ on the growth, homoacetogenesis and corrinoid production by Clostridium thermoacetium was investigated in a glucose-minimal medium. Fe2+, Se4+ and Mo6+ were absolutely required for growth and homoacetogenesis, giving the maximum activities of formate dehydrogenase and of carbon monoxide dehydrogenase. Growth and corrinoid formation were regulated by the presence of Fe2+ in the culture, and its optimum concentration was 100-mu-M. Although Co2+ did not have so much influence on the growth, homoacetogenesis and its acetate/glucose molar yield at concentrations between 0-400-mu-M, the maximum total corrinoid of 9.1 mg/l was produced at 400-mu-M of cobalt nitrate. Electrophoretic identification of the corrinoids revealed that about 22% of total corrinoids was comprised of the Factor IIIm (5-methoxybenzimidazolyl cobamide) and the remainder were mainly the base-free Factor B (cobinamide) and its analogues.