Mixed carbon source utilization of meat-spoiling Pseudomonas fragi 72 in relation to oxygen limitation and carbon dioxide inhibition.

Abstract

The growth of meat-spoiling Pseudomonas fragi 72 was studied on a defined salt medium supplemented with L-aspartate, citrate, creatine, creatinine, D-glucose, L-glutamate, and L-lactate. The utilization of the different carbon sources was followed in batch and continuous culture and under the influence of oxygen limitation and carbon dioxide inhibition (50% CO2 in air). Under nonrestricted atmospheric conditions in batch culture, the organism showed a preference in the utilization of the carbon sources in the order glucose greater than lactate greater than citrate greater than aspartate-glutamate greater than creatine greater than creatinine. The first five sources were utilized simultaneously. The order of preference was changed in continuous culture to lactate-citrate-glutamate-aspartate greater than glucose greater than creatine greater than creatinine. All carbon sources were utilized at lower dilution rates, but as the rate was increased the concentration of the carbon sources started to increase in the effluent and the preference could be seen. Under conditions of oxygen limitation the preference for glucose was weakened, but for lactate it was slightly enhanced (batch and continuous culture). Under conditions of CO2 inhibition, the preference for glucose was enhanced. However, lactate and amino acids were still preferred to glucose in the continuous culture. The utilization of creatine and creatinine was blocked by CO2 in batch culture, and only a slight utilization of creatine was noticed in a chemostat at lower dilution rates.