Biomedical Engineering Reference
In-Depth Information
Process Changes
Replacement of existing chemical methods of production with those based on
microbial or enzyme action is an important potential area of primary pollution
prevention and is one role in which the use of genetically modified organisms
could give rise to significant environmental benefit. Biological synthesis, either by
whole organism or by isolated enzymes, tends to operate at a lower temperature
and, as a result of high enzymatic specificity, gives a much purer yield with
fewer by-products, thus saving the additional cost of further purification. There
are many examples of this kind of industrial usage of biotechnology. In the
cosmetics sector, there is a high demand for isopropyl myristate which is used
in moisturising creams. The conventional method for its manufacture has a large
energy requirement, since the process runs at high temperature and pressure to
give a product which needs further refinement before it is suitable for use. An
alternative approach, using enzyme-based esterification offers a way to reduce
the overall environmental impact by deriving a cleaner, odour-free product and
at higher yields, with lower energy requirements and less waste for disposal.
Textile industry
There is a long tradition of the use of biological treatment methods in the clothing
and textile industry, dating back to the first use of amylase enzymes from malt
extract, at the end of the nineteenth century, to degrade starch-based sizes for
cheap and effective reduction of fabric stiffness and improvement to its drape.
Currently, novel enyzmatic methods provide a fast and inexpensive alternative
to traditional flax extraction by breaking down the woody material in flax straw,
reducing the process time from 7 to 10 days, down to a matter of hours. The
enzyme-based retting processes available for use on hemp and flax produce finer,
cleaner fibres, and, consequently, novel processing techniques are being devel-
oped to take advantage of this. Interest is growing in the production of new,
biodegradable polymeric fibres which can be synthesised using modified soil
bacteria, avoiding the current persistence of these materials in landfills, long
after garments made from them are worn out.
In natural fibre production enzymes are useful to remove the lubricants which
are introduced to prevent snagging and reduce thread breakage during spinning,
and to clean the natural sticky secretions present on silk. The process of bio-
scouring for wool and cotton uses enzymes to remove dirt rather than traditional
chemical treatments and bio-bleaching uses them to fade materials, avoiding
both the use of caustic agents and the concomitant effluent treatment problems
such conventional methods entail. Biological catalysts have also proved effective
in shrink-proofing wool, improving quality while ameliorating the wastewater
produced and reducing its treatment costs, compared with chemical means.
A process which has come to be called bio-polishing involves enzymes in
shearing off cotton microfibres to improve the material's softness and the drape
and resistance to pilling of the eventual garments produced.
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