Mt. Patel et al., CHARACTERISTICS OF LIPASE-CATALYZED HYDROLYSIS OF TRIACYLGLYCEROLS INAEROSOL-OT ISO-OCTANE REVERSE-MICELLAR MEDIA/, Biotechnology and applied biochemistry, 22, 1995, pp. 1-14
In a reverse-micellar system of Aerosol-OT [bis-(2-ethylhexyl) sodium
sulphosuccinate]/iso-octane, triacylglycerols (TAG) could be hydrolyse
d up to 60-98%, depending upon the enzyme source. Hydrolysis reactions
obeyed Michaelis-Menten kinetics and exhibited a linear relationship
of the initial rate with enzyme concentration, which suggests that the
reaction rate in reverse micelle is kinetically controlled and not li
mited by mass-transfer considerations. The kinetic parameters for hydr
olytic reactions are related to enzyme source and physicochemical char
acteristics of substrate. The Michaelis constant (K-m) and maximum rea
ction rate (V-max) for hydrolysis of olive (Olea europaea) TAG by Rhiz
opus javanicus lipase were significantly higher than that by Candida c
ylindracea lipase, The kinetic parameters for coconut TAG were lower t
han that of olive TAG. The K-m and V-max. for TAG hydrolysis increased
with increase in reaction temperature and decreased with increase in
reaction pH. Buffer components may have considerable effect on enzyme
activity and R-activity (R is the molar ratio of water to surfactant)
profile of lipases in reverse micelles. When considering the influence
of reaction variables on lipase-catalysed reactions for practical pur
poses, the initial rate as well as reaction rate over extended periods
of time should be studied. The effect of reaction variables, surfacta
nt concentration as an example, could be different on initial rate and
degree of hydrolysis at 24 h. Lipase activity is rapidly reduced in r
everse-micellar media in absence of any substrate. The effect is sever
e at higher value of R. The stability of enzyme in reverse micelles is
also related to enzyme source. Reverse-micellar systems, in conjuncti
on with other bioseparation techniques, could be used for lipase-catal
ysed bioconversion of TAG and other sparingly-water-soluble compounds
for the production of value-added products.