Reverse micellar extraction: technological aspects, applications and recent developments

The final objective of any bioprocess industry is to obtain product of desired purity with maximum activity recovery especially in case of proteinaceous products. The unit operation involved for the separation and purification of the desired product is known as the downstream processing (DSP). Among various processes reverse micellar extraction (RME) has gained a wide attention in recent years due to its several advantages over other techniques which include ease of scale up, protein separation with maximum activity recovery, continuous operation, biocompatibility, high capacity and off course the cost effectiveness which inherently comes with the recycling opportunity of the organic phase. This review article is a detailed account of the RME system and its applications. The whole tri-component system is mainly composed of solvent, cosolvent and surfactant. The process of extraction is controlled by various factors viz. concentration and type of surfactant, size of the reverse micelle (RM), water content, aqueous phase pH, ionic strength and type, temperature etc. There are three methods of protein solubilisation dry addition, injection and phase transfer. Although it has currently wide range of applications especially in case of food products, integration of RME with the other DSPs has shown promise able results with the increase of protein recovery and purification fold. Recently patents have also been issued on the use of RME in supercritical fluid and in case of extraction of protein from a solid support. Development of reliable RME technique has also been resulted in separation of pharmaceutical grade plasmid DNA from RNA. Potential edge of this technology over others has opened a new field of research for future. Works are required to be done in making the technology friendly for scale up and commercialisation with continuous development in case of more biocompatibility, economic feasibility and better solute transfer rate.