Study on colloidal gas aphrons application in bioprocesses

Colloidal gas aphrons (CGAs) are surfactant-based microbubbles. They are described as microfoamsapproximately 10–100 μm diameter with special structure which is different from that ofconventional foam. Although the size of aphron exceeds that of colloid, which ranges from 1 nm to1 μm, the term colloid is used firstly because of small size of the microfoams and secondly becausethe bubbles show some colloidal properties. They exhibit unique properties which distinguish themfrom conventional foams and are as follows: large interfacial area per unit volume which is beneficialfor the adsorption of molecules, high stability compared with conventional foam, similar flowproperties to those of water e.g. being easily pumped from one place to another, and their easyseparation from the bulk liquid phase due to buoyancy. Because of these properties they have a widespectrum of applications and a large body of research has been published on CGAs applications invarious fields. Application of CGAs in biotechnology has been gaining importance in recent years.Some studies focused on the separating role of CGA systems in bioprocesses and discussed theirusage in separation processes such as protein and enzyme recovery, carotenoids recovery, removalof organic dyes from wastewaters, removal of dispersed oil droplets from water, and cell harvesting.But other sector of literature deals with CGA systems used in mass transfer promoting areas inbioprocesses which include oxygen delivery in bioreactors and bioremediation; that is separation ofhazardous contaminants from soil and water. The main purpose of this article is to review the usageof CGAs in the realm of biotechnology in recent years and to open up new fields.

Keywords:

Colloidal gas aphrons , microfoam , biotechnology , mass transfer , separation