The fixation of CO2 by cell suspensions of Propionibacterium pentosaceum

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Abstract
Fixation of CO2 by cell suspensions of P. pentosaceum was investigated using various substrates. Dissimilation of mannitol, adonitol, erythritol, glycerol and rhamnose under an atmosphere of CO2 was accompanied by uptake of CO2, glyceraldehyde, glucose, dihydroxyacetone, arabinose, galactose and xylose gave a small evolution or some uptake. The evolution of CO2 from lactic and pyruvic acids was much larger. Dissimilation of most of the substrates in an atm. of N2 occurred with an evolution of CO2 which was usually much larger than in an atm. of CO2, indicating utilization of CO2 is proportional to the CO2 conc. These results suggest that the fixation of CO2 may be a phenomenon of widespread occurrence. Malonate, azide, ar-senite, cyanide and pyrophosphate had no influence on C02 fixation. NaF and iodoacetate inhibit CO2 utilization but iodoacetate suppresses the entire dissimilation. NaF increased the evolution of CO2 from a number of substrates. This fact is further evidence of its utilization in their dissimilation. The conc. of NaF necessary to inhibit dissimilation of phosphoglyceric acid was about one-half that required to inhibit utilization of CO2. The reactions inhibited may not be identical in the 2 processes. A phosphate ester, possibly phosphopyruvic acid, is apparently involved in the utilization of CO2.