Formaldehyde uptake by Methylobacterium sp. MF1 and Acidomonas methanolica MB 58 with the different formaldehyde assimilation pathways.

Abstract

Methylobacterium sp. MF1 (an obligate methylotrophic bacterium isolated newly by the authors) and Acidomonas methanolica MB58 (a facultative methylotrophic bacterium) uptake formaldehyde similarly. It was found that the former assimilated formaldehyde via the serine pathway whereas the latter did so via the ribulose-monophosphate pathway from the measurement of the key enzyme activities in each assimilation pathway. That is, hydroxy pyruvate reductase was detected in only the above-mentioned MF1 strain, but hexulose phosphate synthase (HPS) was not. The efficiencies of formaldehyde consumption by both strains under a continuous chemostat cultivation in the steady state were almost the same in spite of their different assimilation pathways. That is, the consumption efficiencies of the MF strain and the MB58 strain were ca. 1.2 g/L/d and ca. 1.8 g/L/d, respectively, under the experimental conditions. In the future, optimal continuous operating conditions will be investigated.