Scale-up of anaerobic 1,3-propanediol production by Clostridium butyricum DSP1 from crude glycerol

Abstract

Background: As the production of biofuels from raw materials continuously increases, optimization of production processes is necessary. A very important issue is the development of wasteless methods of biodiesel production. One way of utilization of glycerol generated in biodiesel production is its microbial conversion to 1,3-PD (1,3-propanediol).

Results: The study investigated the scale-up of 1,3-PD synthesis from crude glycerol by Clostridium butyricum. Batch fermentations were carried out in 6.6 L, 42 L and 150 L bioreactors. It was observed that cultivation of C. butyricum on a pilot scale did not decrease the efficiency of 1,3-PD production. The highest concentrations of 1,3-PD, 37 g/L for batch fermentation and 71 g/L for fed-batch fermentation, were obtained in the 6.6 L bioreactor. The kinetic parameters of 1,3-PD synthesis from crude glycerol established for batch fermentation were similar regarding all three bioreactor capacities. During fed-batch fermentation, the concentration of 1,3-PD in the 150 L bioreactor was lower and the substrate was not completely utilized. That suggested the presence of multifunctional environmental stresses in the 150 L bioreactor, which was confirmed by protein analysis.

Conclusion: The values of effectivity parameters for 1,3-PD synthesis in batch fermentations carried out in 6.6 L, 42 L and 150 L bioreactors were similar. The parameters obtained during fed-batch fermentations in the 150 L bioreactor differed in the rate and percentage of substrate utilization. The analysis of cell proteins demonstrated that a number of multifunctional stresses occurred during fed-batch fermentations in the 150 L bioreactor, which suggests the possibility of identifying the key stages in the biochemical process where inhibition of 1,3-PD synthesis pathways can be observed.

Figure 1

Kinetics of glycerol consumption (filled circles) and 1,3-propanediol production (filled squares) (a); butyric acid (open circles), lactic acid (open squares), acetic acid (open triangles), ethanol (cross), production and biomass growth (stars) (b) during growth of C. butyricum DSP1 in fed-batch in 6.6 L bioreactor experiments.

Figure 2

Kinetics of glycerol consumption (filled circles) and 1,3-propanodiol production (filled squares) (a); butyric acid (open circles), lactic acid (open squares), acetic acid (open triangles), ethanol (cross), production and biomass growth (stars) (b) during growth of C. butyricum DSP1 in fed-batch in 150 L bioreactor experiments.