Effect of CO2 on the fermentation capacities of the acetogen Peptostreptococcus productus U-1

The acetogenic bacterium Peptostreptococcus productus U-1 uses carbon dioxide (CO2) as an electron acceptor to synthesize acetate. Under limited CO2 concentration, P. productus U-1 grown in fructose is observed to synthesize lactate in high amounts as a reduced end product, but in the absence of CO2, the bacteria produces lactate and succinate as reduced end products. In contrast, bacteria grown in glycerol synthesizes high levels of ethanol in the absence of CO2. The results indicate that acetogens undergo fermentation to augment the absence of CO2 during lactate formation.