CHARACTERISTICS OF LIPASE-CATALYZED HYDROLYSIS OF TRIACYLGLYCEROLS INAEROSOL-OT ISO-OCTANE REVERSE-MICELLAR MEDIA/

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.