Lipids in biological matter are mostly triacylglycerols (TAG). Lipolyt
ic enzymes, primarily lipases, are indispensable for bioconversion of
such lipids from one organism to another and within the organisms. In
addition to their biological significance, lipases are very important
in the field of food technology, nutritional and pharmaceutical scienc
es, chemical and detergent industries, and clinical medicine because o
f their ability to catalyze Various reactions involving a wide range o
f substrates. Conventionally, lipases have been viewed as the biocatal
ysts for the hydrolysis of TAG (fats and oils) to free fatty acids, mo
noacylglycerols (MAG), diacylglycerols (DAG), and glycerol. The main a
dvantages of lipase catalysis are selectivity, stereospecificity, and
mild reaction conditions. Despite these advantages and the fact that e
nzymatic splitting of fats for fatty acid production was described as
early as in 1902 the lipase-catalyzed process has not replaced the com
mercial physicochemical process for the continuous splitting of TAG ut
ilizing super-heated steam. The limited exploitation of lipase technol
ogy may be attributed to high enzyme cost, large reaction volume, requ
irement for emulsification of substrate, and risk of microbial contami
nation. Many of these limitations originate from the fact that lipases
are employed mainly in water-rich reaction media where the solubility
of the substrate TAG is very small. To circumvent this problem and to
realize the full potential of lipase, researchers have explored newer
approaches by manipulating the conditions under which the lipases Bet
. Many of these novel approaches for lipase catalysis have been the ou
tcome of the discovery that enzymes can be active in water-poor, non-p
olar media (Hanhan, 1952; Misiorowski and Wells, 1974; Zaks and Kliban
ov, 1984). Also, the finding that lipases can act in organic solvents
has led to an expansion of their applicability in a wide variety of ch
emical reactions. Lipase catalysis in some of the well established rea
ction media has previously been reviewed (Brockerhoff and Jensen, 1974
; Brockman, 1984; Lilly et al., 1987; Halling, 1990; Inada et al., 199
0; Malcata et at, 1990). The present review is intended to present a c
ompilation and comparison of novel reaction systems used for lipase ca
talysis. This review describes briefly the general characteristics of
lipase reactions, applications of lipase in various fields, and conven
tional lipase technology. The lipase-mediated biochemical reactions, p
articularly the hydrolysis of TAG in novel reaction media is discussed
in greater detail.