CHAPTER SEVEN
REVERSED MICELLAR BIOREACTION
SYSTEMS: PRINCIPLES AND
OPERATION
CRISTINA M.L.CARVALHO1,2 AND JOAQUIM M.S.CABRAL^1
(^1) Centre for Biological and Chemical Engineering, Institute Superior
Técnico, Av. Rovisco Pais, 1049–001 Lisboa, Portugal
(^2) Faculdade de Farmácia de Lisboa, Universidade de Lisboa, Av. Prof.
Gama Pinto, 1649–003 Lisboa, Portugal
ABSTRACT
Reversed micelles have been used as a non-conventional medium to
perform biocatalysis. Reversed micelles can be classified as a
“microreactor” where the enzyme is sheltered and protected from solvent
detrimental effects. This is a simplistic idea that led most researchers to
ignore the specificities of this multiphasic system and especially what the
enzyme experiences inside the reversed micelle. This chapter aims to
analyse some of the fundamental aspects related to microencapsulation as
well as to resume progress of the reversed micellar biosystems. The new
trends where efforts should be focused to extend micellar technology to
industrial processes, are also discussed.
The operation of micellar bioreactors (MBRs) is highlighted in terms
of classification and definition of operational caracteristics. The MBR
operation is also analysed as batch and continuous reactors.
REVERSED MICELLAR PRINCIPLES
DefinitionReversed micelles are microheterogeneous systems consisting of an aqueous micro-
domain facing the polar heads of the surfactant that surrounds this core and interacts with
the organic solvent, through the hydrophobic chains. The polar cores of the micelles have
the ability to solubilise a significant amount of water, which depends on the reversed
micellar system properties. When the enzymes are microencapsulated, usually, they are
located in the interior aqueous phase of reverse micelles, although the degree of
interaction with the surfactant interface is variable. This location is assumed to protect the
enzyme from the adverse effects of organic solvent. However, the contact with surfactant
may also be detrimental to the biocatalyst.