Continuous lactose fermentation by Clostridium acetobutylicum—Assessment of energetics and product yields of the acidogenesis

An assessment of both the growth and the metabolism of acidogenic cells Clostridium acetobutylicum DSM 792 is reported in the paper. Tests were carried out in a CSTR under controlled pH conditions. Cultures were carried out using a semi-synthetic medium supplemented with lactose as carbon source. Acids and solvents, that represent products of the ABE process, have been purposely added in controlled amounts to the culture medium to investigate their effects on the product yields. The mass fractional yield of biomass and products were expressed as a function of the specific growth rate taking into account the Pirt model. The maximum ATP yield and the maintenance resulted 29.1 gDM/molATP and 0.012 molATP/gDM h, respectively. Quantitative features of the C. acetobutylicum growth model were in good agreement with experimental results. The model proposes as a tool to estimate the mass fractional yield even for fermentations carried out under conditions typical of the solventogenesis.