MEMBRANE-BASED EXTRACTIVE FERMENTATION TO PRODUCE PROPIONIC AND ACETIC-ACIDS - TOXICITY AND MASS-TRANSFER CONSIDERATIONS

A series of microporous membranes and polymer films was examined for mass transfer performance in the membrane-based extraction of propionic and acetic acids. A range of organic solvents and acid-complexing carriers was screened for toxic effects on a strain of Propionibacterium acidipropionici. Based on these results, more extensive studies were made of the extraction kinetics of tri-n-octylphosphine oxide in the diluents decane and kerosene. After the supported liquid membrane configuration showed problems with stability, the TOPO/kerosene in Celgard X-20 microporous membrane system was chosen for use in an extractive fermentation with the membrane between the fermentation broth and bulk extractant in a hollow fiber module.