Cuphea Production and Management - Industrial Crops: Breeding for BioEnergy and Bioproducts - page 290

Fatty Acid Synthesis in Cuphea Seeds

The biosynthesis of MCFA in Cuphea lanceolata starts with the carboxylation of
acetyl-CoA by the enzyme acetyl-CoA carboxylase to form malonyl-CoA, a path-
way common to all plant species. The initial condensation between acetyl-CoA and
malonyl-ACP (acyl-carrier protein)

is catalyzed by the enzyme KAS III

( -ketoacyl-acyl-ACP synthase III) [ 27 ]. In most plants, further chain elongation

is catalyzed by acyl-ACP-specific condensing enzymes, KAS I (C6 to C16) and
KAS II (C16 to C18). In cuphea, there is a KAS IV enzyme responsible for MCFA
synthesis that interacts with specific medium-chain thioesterases that hydrolyze the
ACP and release the fatty acid stopping the elongation at C10 or C12 [ 28 ]. The
increased pool sizes of medium-chain acyl-ACP inhibit the condensation of KAS
enzymes downstream after KAS III, then KAS IV is responsible for catalyzing the
elongation to C10. The ACPs play an important role in plant fatty acid synthesis
since they carry the acyl moieties during fatty acid elongation [ 29 ]. Different ACP
forms exist in plants with at least three specific ACPs identified in Cuphea
lanceolata [ 30 ]. C. lanceolata has a specific ACP isoform (ACP2) compatible
with medium-chain fatty acid thioesterase to optimize the synthesis of MCFAs [ 29 ].

β

Cuphea Oil Uses

Medium-chain fatty acids can be used to replace saturated fatty acids and plasti-
cizers in chewing gum. Cuphea oil also works well as a flow carrier and solvent in
candy manufacturing and as a defoaming agent and booster in soap and detergent
manufacturing [ 31 ]. Cuphea oil can be used in high-valued cosmetic products such
as lipsticks, lotions and creams, and bath oils [ 32 ]. The oil has a high oxidative
stability, low- to medium-spreading ability, and low slip value, all of which provide
the desirable non-slippery characteristic for use in sunscreens [ 33 ].
The properties of cuphea oil make it ideal for advanced biofuels including
biodiesel and jet fuel [ 34 ]. Because of the already short carbon chain lengths of
cuphea seed oil triglycerides, it lends itself well to the manufacture of jet fuel with
little chemical modification. The addition of cuphea oil to jet fuel reduces the fuel's
freezing point avoiding fuel-gelling flow at temperatures below

20 C. The long-
term use of biodiesel from unmodified vegetable oil from soybean ( Glycine max
(L.) Merr.) and rapeseed ( Brassica napus L.) can result in the buildup of carbon
deposits (coking) on the engine fuel injectors due to incomplete combustion that
causes deterioration of engine performance. Therefore, transesterification is needed
to break the oil into fatty acid esters and glycerol. Fatty acid esters burn cleanly and
efficiently in the engine, but glycerol must be removed and this process is costly.
Oils rich in short- and medium-chain fatty acids have a reduced viscosity so they
can be used as a diesel fuel substitute without

transesterification. Oil from