Feasibility of supported emulsion liquid membrane extraction for fermentation media rejuvenation

Continuous extractive fermentation offers many advantages over batch processes. Among them, the most attractive feature is that the integrated removal of product can reduce inhibiting effects and hence increase productivity. Using Propionibacteria as the model system, the feasibility of using supported emulsion liquid membrane (SELM) for extractive fermentation is assessed in this study. It was demonstrated that SELM removes the equilibrium limit encountered in the simple extraction and allows the usage of solvent with no toxic effect on Propionibacteria.; The main design consideration for extractive fermentation is the selection of solvent. An ideal solvent for extractive fermentation must have a favorable partition coefficient for the desired compounds, low viscosity, good membrane material compatibility and a minimal toxic effect on the microorganism. Unfortunately, these conditions often compete with each other and a compromise must be made. Various solvents were evaluated and tetradecane is suggested to be the optimal solvent to carry out the feasibility study.; Various modules from different manufactures were evaluated in this research. One hydrophobic module (Enka LM-2P06, Microdyn) gives robust behavior in SELM extraction. Although the experimental results indicate that hydrophilic module removes propionic acid much faster than the hydrophobic module, none of the hydrophilic modules were robust enough to carry out SELM extraction in long term studies. CellmaxRTM artificial capillary cartridges 400-023 was found to be the best hydrophilic module candidate since it went through three SELM extractions before the mechanical failure occurred. Film mass transfer theory and parameters were used to characterize the mass transfer rate in the hydrophobic module as well as the leading hydrophilic module candidate. The model prediction gave excellent agreement with the experimental data for hydrophobic module and it was three times lower than the experimental data for hydrophilic module.; An attempt was made to recycle real fermentation media using SELM. The result suggested that 80% recycle ratio may be too high to allow P20 to grow if only one half of the propionic acid is removed. A hydrophobic module with larger membrane area is required to carry out SELM extraction in a reasonable time.