Liquid emulsion membrane biochemical separations

Kitagawa, T. Nishikawa, Y. Frankenfeld, J. W. Li, N. N. "Wastewater Treatment by Liquid Membrane Process" Environ. Sci. Tech. 1977,11, pp 602-605. Thien, M. P. Hatton, T. A. Wang, D. I. C. "Liquid Emulsion Membranes and Their Applications in Biochemical Separations" In Separation, Recovery, and Purification in Biotechnology ACS Symposium Series 314, 1986, pp 67-77. 

Liquid Emulsion Membranes and Their Applications in Biochemical Separations... 

Applications of liquid emulsion membranes (LEMs) to biomedical and biochemical systems are reviewed and other potential applications identified. The LEM-mediated downstream processing of small, zwitterionic biochemicals (e.g. amino acids) is examined using chloride ion counter-transport to separate and concentrate the amino acid phenylalanine from stimulated fermentation broth. The effect of agitation rate and osmotic swelling of membranes on separation is shown to be significant. 

LEM systems have also been shown to be successful in separating commodity-type biochemicals such as propionic acid (10) and acetic acid (10,22) and have been used for the preparation of L-amino acids from racemic D,L mixtures by means of enzymatic hydrolysis of amino acid esters (23). In addition to biochemical separations, the work of Mohan and Li showed that enzymes could be encapsulated in liquid emulsion membranes with no deleterious effect on enzyme action (24). Later work by these authors indicated that encapsulated live cells could remain viable and function in the LEM interior phase for period as long as five days (25). 

These various uses of liquid emulsion membranes show the versatility of LEM-mediated separations and point to possible applications of liquid emulsion membranes in the biochemicals field. 

The versatility of LEMs is clear. From the encapsulation of living cells to the removal of toxic or inhibiting substances, and in their use as a downstream process, liquid emulsion membranes remain a powerful and, as of yet, virtually untapped resource for biochemical engineers. The ability of LEMs to separate and concentrate amino acids demonstrated here gives strength to this observation, and it is anticipated that these systems will enjoy increasing attention in the years to come. 

In the next section, four chapters describe three main configurations of liquid membranes supported, emulsion, and bulk LM. Each chapter is subdivided into theory and transport mechanisms, module design and experimental techniques, and applications in different fields of chemical, biochemical, environmental, and pharmaceutical separations. 

Bayraktar, E. (2001). Response surface optimization of the separation of dl-tryptophan using an emulsion liquid membrane. Process Biochem., 37, 169-75. 

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