MEMBRANE SEPARATION FOR DOWNSTREAM PROCESSING OF AQUEOUS-ORGANIC BIOCONVERSIONS

The use of membranes to separate liquid/liquid mixtures downstream of multiphasic biocatalytic reactor has been examined. Hydrophilic and hy drophobic membranes were used to separate multiphasic organic solvent/ water mixtures. It was found that one phase could be separated from th e mixture as long as the breakthrough pressure, derived from the Lapla ce law, was not exceeded. The breakthrough pressure was found to be a function of the pore diameter and the interfacial tension. The flux th rough the membranes was found to be function of the volume fraction of water. Between a water volume fraction of 0.4 and 0.8, both hydrophil ic and hydrophobic membranes were found to give high fluxes in the abs ence of surface active material. Yeast and Pseudomonas putida were use d as examples of microbial material present in liquid/liquid mixtures downstream of a multiphasic biocatalytic reactor. The fluxes of both m embranes decreased upon addition of the cells to the mixture. While th e hydrophilic membranes were reversibly fouled and retained acceptable fluxes, in contrast, the hydrophobic membranes were fouled irreversib ly. Subsequently, the hydrophobic membranes were modified and the flux through the hydrophobic modified membrane remained high and was a fun ction of the viscosity and solvent volume fraction. Both hydrophilic a nd hydrophobic membranes could also be used at high pressure when both liquids permeated the membrane. In this case, the membranes acted as coalescence filters although at a considerably reduced flux compared t o low-pressure applications.