The utilization of CO2 by the propionic acid bacteria

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Abstract
Previous exps. showing utilization of CO2 by Propioni-bacterium fermenting glycerol were confirmed and extended. The C of the utilized CO2 was found in the products[long dash]succinic, propionic and acetic acids and propyl alcohol. Total C detns. before and after fermentation show that there is an increase in the total organic C of the medium equivalent to the decrease in inorganic C(CO2). The uptake of gaseous CO2 was sufficient to create a partial vacuum in the apparatus. The succinic acid formed and CO2 utilized were approx. equimolar. Formation of succinic acid is probably by synthesis from a 3-C compound through addition of CO2. In absence of CO2 little or no succinic acid is formed. The relative proportions of the products varied with time and the CO2 utilized. The succinic acid formed increased while the propionic acid decreased.[long dash]Utilization of CO2 by heterotrophic bacteria is considered in connection with other reactions proposed for the formation of succinic and citric acids.