DEVELOPMENTS TOWARD LARGE-SCALE BACTERIAL BIOPROCESSES IN THE PRESENCE OF BULK AMOUNTS OF ORGANIC-SOLVENTS

Many pseudomonads and other bacteria can grow on aliphatic and aromati c hydrocarbons that occur in the environment. We are examining the pot ential of such organisms as biocatalysts for the oxidation of a variet y of substituted aliphatic and aromatic compounds. To attain a high pr oduction rate of oxidation products via such biotransformations, we ha ve focused on two-liquid phase culture systems, In these systems? cell s are grown in liquid media consisting of an aqueous phase containing water-soluble growth substrates and droplets of a water-immiscible org anic solvent containing bioconversion substrates and products. For ind ustrial applications of such two-liquid phase processes, several quest ions remain. What are the maximum rates at which apolar compounds can be transferred from the apolar phase to cells growing in the aqueous p hase, i.e., what are the maximum space-time yields attainable in two-l iquid phase fermentations under practical conditions? What does an eff icient downstream processing of two-liquid phase medium involve? What safety regimes should be considered in working with flammable organic solvents? Can elevated pressure be used to increase oxygen transfer? B ased on answers to these questions, we have recently developed a high- pressure, explosion-proof bioreactor system with Bioengineering AG (Wa ld, Switzerland), which will be installed in our pilot plant and used to explore two-liquid phase bioconversions at a pilot scale.