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

Jul 11, 2012 by Journal of Biotechnology and Biomaterials

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. To implement a strategy of successful fermentation allowing optimizing the production of 1,3-Propanediol, the kinetic characteristics of conversion of the glycerol at Clostridium butyricum were studied. The aim of this work was to make kinetic studies on the production of the 1,3-Propanediol from the glycerol by Clostridium butyricum and to study the influence of the parameters of environment (initial content in glycerol and feed flow) on the behavior of this strain. This method allowed defining the best conditions of growth and production of the 1,3-Propanediol. Different fed batch strategies were realized on glycerol as only source of carbon and energy; they began
with weak and strong initial contents in glycerol and fed with weak and strong flow of glycerol, allowed us to retain different behaviors of Clostridium butyricum. According to obtained results, we can conclude that the pathway of production of the 1,3-Propanediol is associated to the one of some butyric acid. The accumulation of the glycerol in the fermentation medium provokes a disorientation of the Clostridium butyricum cellular metabolism towards the pathway of production of the acetic acid and contribution controlled by substratum in the fermentation medium allows the production of an important quantity of 1.3-Propanediol and butyric acid. This accumulation of the glycerol in the fermentation medium blocks and inhibits assimilation of the glycerol in the internal of the cell, which provokes a very strong decrease of kinetic parameters and yield on conversion of the glycerol in 1,3-Propanediol and butyric acid. The modeling showed a big resemblance between the experimental reality and the realized model.