Biotechnological methods:
For microbial dye decolourisation not connected to the activated sludge
process, bioreactors can be designed containing defined bacterial or fungal
cultures, isolated enzymes or enzyme mixtures immobilised on a solid
212 Textile processing with enzymes
carrier material. Such immobilised biocatalysts are much more susceptible
to damage by harsh chemical environments than are the mixed cultures
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| Biotechnological methods |
present in activated sludge systems. Thus, they are preferentially used to
treat partial process streams within the plant where the composition and
physical properties are rather more readily controlled than the overall plant
effluent.
For instance, exhausted dyeing bath solutions have been decolourised
enzymatically using a laccase formulation and subsequently reused for the
preparation of new dyeing baths (Abadulla et al., 2000). Similarly, hydrogen
peroxide has been removed enzymatically from bleaching solutions
using a catalase in an industrial pilot experiment . Owing
to the use of high-specificity enzymes, only the target molecules are
attacked while valuable additives or fibres are kept intact and can be
reused.
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