Environmental Engineering Reference
In-Depth Information
Polyunsaturated fatty acids are known to have an effect on serum cholesterol in
humans [43]. The hypocholesterolemic effect of linoleic acid has been well estab-
lished [50-52]. Horrobin and Huang have shown that increasing the intake of
linoleic in one's diet leads to a reduction in plasma cholesterol, though large
amounts need to be consumed [53]. It is thought that a metabolite of linoleic acid,
which is metabolised in the body via a number of routes, brings about this choles-
terol-lowering effect. Studies have shown that in normolipidemic men, α-linolenic
acid is just as effective in lowering blood cholesterol as linoleic acid [54]. Research
has shown that different types of diets, which varied in the composition of unsatu-
rated fatty acids, had similar cholesterol-lowering results.
Policosanols have a wide variety of potential applications, most notably in the
prevention and treatment of a variety of cardiovascular-related conditions such as
poor arterial function, hypercholesterolemia, poor antioxidant status and intermit-
tent claudication [49]. Policosanol supplements are shown to lower the levels of
cholesterol [54]. It has also been suggested that policosanols can act as potent
antioxidants, inhibiting low-density-lipoprotein (LDL) -cholesterol peroxidation
[49, 54]. Apart from medicinal uses, policosanols may also have potential cos-
metic applications. Policosanols were found to be ideal components in cosmetics
as anti-acne agents, as an emollient and for the control of sebum secretion [48].
Phytosterols are of particular interest as they have a variety of potential bio-
logical and physiological applications. The three main phytosterols that are pre-
sent in the human diet are β-sitosterol, campesterol and stigmasterol [47]. They
are widely known to act as efficient anticancer compounds. It has been estimated
that the risk of cancer can be significantly decreased by as much as 20% with a
phytosterol-enriched diet.
The high molecular weight of wax esters makes them one of the most signifi-
cant groups of molecules found in plant waxes. This is because the high molecular
weight allows for many valuable applications ranging from cosmetics to hard wax
polishes, lubricants, coatings and plasticisers [46].
Sugarcane bagasse has therefore shown to be a promising feedstock for the
generation of added-value products. Another significant agricultural residue in the
world is wheat straw. The world production of wheat grain in 2010 was estimated
to be 651.8 million tonnes by the FAO in 2011. Every tonne of wheat grain leads
to the generation of 1.3 tonnes of wheat straw, which is of low economic value
[55]. This by-product is extensively used in livestock feed and bedding; however,
there is a growing interest in utilising wheat straw as a biomass feedstock for use
in the production of fuel sources such as bioethanol. The main component of
wheat straw that is used in biofuel production is the lignocellulosic component
[56, 57]. However, also present in wheat straw are a large range of secondary
metabolites that have potential economic value [58].
The epicuticular wax that coats the surface of the wheat straw (1% w/w) can
generate a number of high-value products [28, 59]. The use of supercritical carbon
