ACETOGENESIS COUPLED TO THE OXIDATION OF AROMATIC ALDEHYDE GROUPS

Vanillin cultures of Clostridium formicoaceticum produced higher cell densities than did vanillate cultures. During growth at the expense of vanillin, vanillate was the predominant intermediate formed; 3,4-dihy droxybenzaldehyde was not a significantly detectable intermediate. Ace tate and protocatechuate were both produced in equimolar ratio relativ e to vanillin consumption. 4-Hydroxybenzaldehyde was a growth-supporti ve aromatic compound for both C. formicoaceticum and Clostridium aceti cum (doubling times approximated 5 h), was oxidized stoichiometrically to 4-hydroxybenzoate, and was not appreciable toxic at concentrations up to 15 mM. Acetate was (i) the major reduced end product detected c oncomitant to growth and to benzaldehyde oxidation and (ii) formed in close approximation to the following stoichiometry : 4 4-hydroxybenzal dehyde + 2 CO2 + 2H2O --> 4 4-hydroxybenzoate + CH3COOH. We conclude t hat these two acetogens are capable of benzaldehyde-coupled acetogenes is and growth.