78 Environmental Biotechnology
could give rise to significant environmental benefit. Biological synthesis, either by
whole organisms or by isolated enzymes, tends to operate at lower temperatures
and, as a result of high enzymatic specificity, gives a much purer yield with
fewer byproducts, 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 seven to ten 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
developed 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 bioscour-
ing 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 biopolishing 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.
Biostoning has been widely adopted to produce ‘stone-washed’ denim, with
enzymes being used to fade the fabric rather than the original pumice stone
method, which had a higher water consumption and caused abrasion to the denim.