secretion of extracellular ligninol

secretion of extracellular ligninolytic enzymes during their
secondary metabolism in response to nutrient limitation,
namely lignin peroxidase (ligninase, LiP, EC 1.11.1.14),
manganese peroxidase (MnP, EC 1.11.1.13) and laccase
(benzenediol/oxygen oxidoreductase, EC 1.10.3.2).
The major drawback to using an enzyme preparation is that
once the enzymes become inactivated, activity decreases. In
addition, the high cost of these enzymes limits their
application to an industrial scale. However, with a wholecell
culture, the enzymes can be continually replenished. In
industrial operations, immobilised microbial cell systems
could provide additional advantages over freely suspended
cells such as easy separation of cells from the liquid medium,
protection from shear damage and reduction in protease
activity. In addition, immobilised cultures are more resilient to
environmental perturbations, such as pH or exposure to toxic
chemical concentrations, than suspension cultures (Shin et al.
2002). Physical entrapment is the most widely used
technique for immobilisation of whole cells and alginate is
a suitable matrix material because it is non-toxic and the
method used for its gelation is mild towards the microorganisms
(Sriamornsak 1998; Cohen 2001; Kourkoutas et
al. 2004). Accordingly, immobilisation into alginate beads
was selected to perform the present study. Previous studies
on azo dye decolouration have mostly been focussed on
reactive azo dyes. Here, the decolouration of four commercial
textile azo dyes belonging to the acid, direct, reactive
and basic classes by Phanerochaete chrysosporium immobilised
into alginate beads was investigated. Reusability of
the alginate-immobilised fungus after a storage period was
also tested. To the best of our knowledge, this is the first
study on the immobilisation of P. chrysosporium into Caalginate
beads for its application in dye decolouration.