Potential application of perfusion and pertraction for in situ product removal in biocatalytic 2-phenylethanol production

Abstract

Abstract Bioproduction of 2-phenylethanol from l -phenylalanine using Saccharomyces cerevisiae is affected by strong product inhibition and thus the maximum reachable concentration in an ordinary batch or fed-batch bioreactor is only about 4 g L −1 . To minimize the effect of product inhibition and to prolong the production period, continual removal of 2-pehnylethanol can be applied. For product removal, adsorption in a fixed bed column can be used but to prevent the column from biomass pollution, a separation method for obtaining a cell free aqueous phase had to be employed before the adsorption step. In this work, the applicability of perfusion and pertraction for obtaining the cell free fermentation medium is studied. Performance of both processes was studied in a series of kinetic measurements with varying concentrations of biomass in a model solution. In case of pertraction, long term stability of supported liquid membrane created by octane was examined. Also, mathematical models of pertraction and perfusion have been verified with experimental measurements. In perfusion experiments, membrane fouling occurred due to the biomass present in feed phase. On the contrary, the biomass did not affect the mass transfer rate during the pertraction. Pertraction was found to be more stable since pores of the membrane are protected from fouling by octane which creates a supported liquid membrane. Octane also forms a barrier for other compounds found in the fermentation medium and can be used for selective transport of 2-phenylethanol to a cell free aqueous solution.