Fermentation parameters of Peptostreptococcus productus on gaseous substrates (CO,H2/CO2)

Intrinsic growth and substrate uptake parameters were obtained for Peptostreptococcus productus, strain U-1, using carbon monoxide as the limiting substrate. A modified Monod model with substrate inhibition was used for modeling. In addition, a product yield of 0.25 mol acetate/mol CO and a cell yield of 0.034 g cells/g CO were obtained. While CO was found to be the primary substrate, P. productus is able to produce acetate from CO₂ and H₂, although this substrate could not sustain growth. Yeast extract was found to also be a growth substrate. A yield of 0.017 g cell/g yeast extract and a product yield of 0.14 g acetate/g yeast extract were obtained. In the presence of acetate, the maximum specific CO uptake rate was increased by 40% compared to the maximum without acetate present. Cell replication was inhibited at acetate concentrations of 30 g/l. Methionine was found to be an essential nutrient for growth and CO uptake by P. productus. A minimum amount of a complex medium such as yeast extract (0.01%) is, however, required.