Novel Products of the Acidogenic Fermentation of Methanol during Growth of Eubacterium limosum in the Presence of High Concentrations of Organic Acids

SUMMARY: Methylotrophic growth of Eubacterium limosum, a fermentative anaerobe, necessitates the production of butyric acid in quantities proportionate to the methanol dissimilatory flux in order to balance the reducing equivalent status of the cell. Supplementing the medium with low concentrations (<100mM) of butyrate decreased the quantity of methanol dissimilated and brought about a corresponding shift in organic acid production in favour of acetic acid. At higher supplement concentrations the growth rate decreased and synthesis of caproic acid and an unidentified compound, most likely a biopolymer, occurred. In fed-batch cultures similar levels of butyrate were necessary to bring about these biotransformations. The addition of a C2-unit to supplemented organic acids was not restricted to those acids normally involved in the acidogenic metabolism of E. limosum, a finding, which may be of potential biotechnological importance.