Biotecnologia e Biomateriais

Abstrato

1,3-Propanediol Production by Clostridium Butyricum in Various Fed- Batch Feeding Strategies

Hariri Ahmed, Ouis Naouel and Bouhadi Djilali

The aim of this study is to propose different fed-batch strategies during the fermentation of glycerol into 1,3-Propanediol, which show the influence of the initial concentration in glycerol and the feed flow on the behaviour of Clostridium butyricum . The kinetic study of the conversion of glycerol into 1,3-Propanediol by Clostridium butyricum , showed that according to the initial concentration of glycerol and feed flow, this strain displays two different metabolic behaviours. This strain directs its metabolism towards its traditional metabolic pathways (production of 1,3-Propanediol, butyric and acetic acid), when the culture was started with a high initial concentration of glycerol and was fed with a weak rate. The high initial concentration of glycerol causes a deceleration of growth rate, which led to an increase in the growth phase duration. Feeding by a weak flow allowed maintaining the cells in full growth phase by providing the necessary substrate for its growth and its maintenance and, at the same time, to avoid the glycerol accumulation in the medium. A high feed flow involved a glycerol accumulation in the culture medium, which obliged the bacterium to direct its metabolism towards the production of acetic acid in significant quantities. The growth phase always showed the same duration, yielding similar final concentrations in biomass and metabolites, an identical metabolic behaviour was observed when the culture begin with a low initial concentration of glycerol, and whatever the flow of substrate applied. This behaviour may be explained by a growth inhibition caused by the accumulation of 1,3-Propanediol in concentrations of 20-25 g/L.