METABOLISM OF AROMATIC-ALDEHYDES AS COSUBSTRATES BY THE ACETOGEN CLOSTRIDIUM-FORMICOACETICUM

When the acetogen Clostridium formicoaceticum was cultivated on mixtur es of aromatic compounds (e.g., 4-hydroxybenzaldehyde plus vanillate), the oxidation of aromatic aldehyde groups occurred more rapidly than did O-demethylation. Likewise, when fructose and 4-hydroxybenzaldehyde were simultaneously provided as growth substrates, fructose was utili zed only after the aromatic aldehyde group was oxidized to the carboxy l level. Aromatic aldehyde oxidoreductase activity was constitutive (a ctivities approximated 0.8 U mg(-1)), and when pulses of 4-hydroxybenz aldehyde were added during fructose-dependent growth, the rate at whic h fructose was utilized decreased until 4-hydroxybenzaldehyde was cons umed. Although 4-hydroxybenzaldehyde inhibited the capacity of cells t o metabolize fructose, lactate or gluconate were consumed simultaneous ly with 4-hydroxybenzaldehyde, and lactate or aromatic compounds lacki ng an aldehyde group were utilized concomitantly with fructose. These results demonstrate that (1) aromatic aldehydes can be utilized as cos ubstrates and have negative effects on the homoacetogenic utilization of fructose by C. formicoaceticum, and (2) the consumption of certain substrates by this acetogen is not subject to catabolite repression by fructose.