Liquid emulsion membranes: principles, problems and applications in fermentation processes.

Liquid emulsion membranes (LEMs) have developed into a versatile technique for a variety of applications involving selective and controlled transport of biochemicals. Biological applications cover the controlled delivery of drugs from capsules, detoxification of the circulatory system, recovery of useful compounds from waste streams and selective separation of products from fermentation broths. This review traces the development of LEMs, discusses their key features, advantages and limitations, describes methods of modelling LEM systems and highlights some applications with industrial potential. Two kinds of LEM systems are considered. The first type are agitated emulsions, which are relatively easy to prepare and use but may be limited in their selectivity and long-term stability. Supported liquid membranes (SLMs) are a recent development; they use porous solid supports and have excellent stability and selectivity. Their chemical engineering aspects and applications in fermentation processes are considered.