Fermentation of glycerol by Clostridium pasteurianum - batch and continuous culture studies

The fermentation of glycerol by Clostridium pasteurianum was studied with r espect to product formation as influenced by the culture conditions. In the majority of batch cultures, butanol was the main fermentation product, but a varying fraction of glycerol was also converted to 1,3-propanediol, buty ric and acetic acids and ethanol. More than 60 g/l glycerol was utilized, a nd up to 17 g/l butanol was produced. Fed-batch cultures did not offer an a dvantage. When molecular nitrogen was used as a nitrogen source, the fermen tation time was prolonged by a factor of 1.5. Fermentations at constant pH values between 4.5 and 7.5 did not reveal significant differences in produc t formation except for an increase in the ethanol content starting at pH 6. 5. Chemostat cultures also yielded predominantly n-butanol, but in some fer mentations, the 1,3-propanediol fraction was relatively high. The pH auxost at cultures, which were operated at a glycerol excess, contained 1,3-propan ediol as the main product. As a whole, the fermentations were characterized by a certain variability in product formation under seemingly equal or sli ghtly varied conditions. It appears that the regulation of the numerous fer mentation pathways occurring in this organism is not very strict.