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UCT RESEARCH REPORT 2012
Dr Anwar Jardine’s research group in UCT’s Department
of Chemistry has been investigating chitosan, derived
from chitin, a natural polysaccharide that is the second
most abundant organic source on earth. Chitin is partly
responsible for the robust hard shell or exoskeleton of
insects and crustaceans, with a structure that is similar
to cellulose.
Chitin and chitosan have an array of potential
applications, and numerous products have already
reached the market for the treatment of a variety
of diseases, including arthritis, inflammatory bowel
disease, and general inflammatory damage.
The growth of the chitin and the chitosan market
worldwide is propelled by the new manufacturing
technologies and expansion in the application domain
– these new, high-end products are worth considerably
more than the low-cost polymers that previously
dominated the industry, spurring on innovation.
Innovation
The Chemical ‘Chameleon’, Versatile Chitosan makes
for an Array of Potential Applications
Dr Jardine and his team have modified chitosan by
converting the 6-hydroxy group in the polymer to a
6-amino group, turning a sparingly soluble polymer into
one that is now completely soluble in aqueous media.
This forms the basis of a patent that has recently been
granted in the USA, with other patent applications
pending. Solubility in aqueous solutions has broadened
the scope of application, particularly in “green”
technologies that seek to replace or minimise the use of
organic solvents in chemical processes.
The main source of the raw material is the shell of the
Southern Spiny Lobster,
Palinarus gilchristi
, after removal
of the tail for sale. It is estimated that in South Africa about
440 tons of this waste are available. This shell exoskeleton
can be transformed into a backbone of another sort – a
soluble, modified chitosan “backbone” molecule that
can be used as a chemical catalyst support. The team
added a platinum group metal catalyst to this novel
chemical backbone, enabling efficient, heterogeneously
catalysed synthesis of fine chemicals in “green” solvent
systems, the subject of a further patent.
Currently, waste shells are either discarded while at sea, or
landed and sold locally as flavouring agents at between
R5 and R10 per kilogram. Although the yield of high-
quality chitosan is only 3 to 5% based on wet-shell weight,
the potential market value of up to R3000/kg chitosan is
attractive and higher-value-added derivatives are even
more enticing.
The modified backbone is currently being explored in a
water purification application for the reduction of high