Long-term production of soluble human Fas ligand through immobilization of Dictyostelium discoideum in a fibrous bed bioreactor

Extracellular polymer substances and the heterogeneity of Clostridium acetobutylicum biofilm induced tolerance to acetic acid and butanol

Extracellular polymer substances limited the transfer of harmful substances, and thus diluted their concentration in order to protect biofilm cells, enabling the maintenance of stability and increased tolerance to environmental stress.

Enhanced propionic acid production from Jerusalem artichoke hydrolysate by immobilized Propionibacterium acidipropionici in a fibrous-bed bioreactor

Propionic acid is an important chemical that is widely used in the food and chemical industries. To enhance propionic acid production, a fibrous-bed bioreactor (FBB) was constructed and Jerusalem artichoke hydrolysate was used as a low-cost renewable feedstock for immobilized fermentation. Comparison of the kinetics of immobilized-cell fermentation using the FBB with those of fed-batch free-cell fermentation showed that immobilized-cell fermentation gave a much higher propionic acid concentration (68.5 vs. 40.6 g/L), propionic acid yield (0.434 vs. 0.379 g/g) and propionic acid productivity (1.55 vs. 0.190 g/L/h) at pH 6.5. Furthermore, repeated batch fermentation, carried out to evaluate the stability of the FBB system, showed that long-term operation with a high average propionic acid yield of 0.483 g/g, high productivity of 3.69 g/L/h and propionic acid concentration of 26.2 g/L were achieved in all eight repeated batches during fermentation for more than 200 h. It is thus concluded that the FBB culture system can be utilized to realize the economical production of propionic acid from Jerusalem artichoke hydrolysate during long-term operation.

Bioreactors for bone tissue engineering

Bone tissue engineering is a promising solution for patients with bone defects that require reconstruction. This regenerative therapy consists in culturing osteogenic cells on a biodegradable substrate to obtain a bio-hybrid construct that will stimulate bone healing after implantation. This multidisciplinary technology nevertheless requires further development before it can become routine clinical practice. One challenge is to achieve three-dimensional seeding and osteogenic commitment of mesenchymal stem cells on biomaterials under sterile and reproducible conditions. For this purpose, different dynamic culture systems have been developed. This paper reviews recent advances in the field of bioreactors for bone tissue engineering. The purpose of such systems is to improve nutrient delivery to the cells and generate shear stress that may promote cell differentiation into osteoblastic phenotypes. A brief overview of the value of computational fluid dynamics for understanding the cell environment is also provided. Finally, some proposals are made regarding the use of bioreactors as safe and controllable devices that will help commit cells and biomaterials for the regeneration of bone tissue.

Control and optimization of Clostridium tyrobutyricum ATCC 25755 adhesion into fibrous matrix in a fibrous bed bioreactor

The great performance of a fibrous bed bioreactor (FBB) is mainly dependent on the cell adhesion and immobilization into the fibrous matrix. Therefore, understanding the mechanism and factors controling cell adhesion in the fibrous matrix is necessary to optimize the FBB setup and further improve the fermentability. The adhesion behavior of a strain of Clostridium tyrobutyricum isolated from an FBB was studied, which was proven to be affected by the different environmental conditions, such as growth phase of cells, pH, ionic strength, ionic species, and composition of media. Our results also suggested that electrostatic interactions played an important role on bacteria adhesion into the fibrous matrix. This study demonstrated that the compositions of fermentation broth would have a significant effect on cell adhesion. Consequently, a two-stage glucose supply control strategy was developed to improve the performance of FBB with higher viable cell density in the operation of the FBB setup.