Kinetics and physiological implications of the growth behaviour of Eubacterium limosum on glucose/methanol mixtures

SUMMARY: Batch-mode growth rates of the acetogenic anaerobe Eubacterium limosum on various substrates were dependent on the point of entry into the central metabolic network. During batch growth on glucose/methanol mixtures, simultaneous consumption of both substrates occurred at residual glucose concentrations below 6 mM following an initial period of growth on glucose alone. During this mixotrophic growth phase, significantly higher biomass yields and specific growth rates were obtained than on either substrate alone. This phenomena was confirmed in chemostat experiments and stoichiometric analysis based on specific rates indicated that carbon and energy flow was significantly altered during mixotrophic growth with little net flux through the pyruvate ferredoxin oxidoreductase. It is suggested that such an effect on both growth rate and biomass yield was due to the improved availability of both carbon and energy for anabolic reactions.