glycerolysis of olive oil in a CSTR with an ultrafilter membrane (polysulfone) to retain
the lipase immobilised on liposomes in reversed micelles. The half-life of the
Chromobacterium viscosum was 7 weeks. Luthi and Luisi 1984 performed the enzymatic
synthesis of hydrocarbon-soluble peptides in a micellar reactor where the (α-
chymotrypsin containing micelles were entrapped in semipermeable hollow fibers. Luisi
and Laane (1986) used a flow hollow-fibre membrane reactor that was semi-permeable,
retaining enzyme and micelles while the small molecules of substrate and products
passed freely. Nevertheless, this type of reactor did not retain the surfactant molecules
due to the dynamics of micelle formation that would inevitably contaminate the product
solution (Khmelnistky et al., 1988).
Cutinase performance was also evaluated in a MBR (Figure 7.3). Cutinase was
microencapsulated in AOT reversed micelles following the optimisation of cutinase
stability studies (Carvalho et al., 1997, 1999a): W 0 2.7 and 1M hexanol. A ceramic
membrane of 15,000 Da MWCO was used. The MBR was continuously operated for five
weeks maintaining the level of 60% conversion and leading to an estimated cutinase half
life of 674 days, which represents an enhancement of 4.2 fold when compared with the
thermostability of microencapsulated cutinase in the presence of 1 M hexanol (Carvalho
et al., 2000a, c, d).
The choice of membrane bioreactors is based on their capacity to retain the enzyme,
and this confinement is mainly a function of the pore size of membranes—usually
ultrafiltration membranes. The productivities achieved are usually high as are the
enzymatic half-lives.
Reversed micellar bioreaction systems 209