In this stage of research, it was investigated whether the
alginate-immobilized C. gallica laccase could be successfully reused
after storage at 4 C. Reusability of immobilized enzymes in
the biodegradation process exhibits the most important aspect for
industrial applications, since it decreases the cost of the process.
Thus, the reusability of the immobilized laccase in seven successive
batches of 24 h each was investigated. The relative decolorization
rates are depicted in Fig. 6. From data in the above figure, it can be
detected that after the 4th cycle, the relative decolorization values
for tested dyes were found to be more than 70% except BBR (51.2%)
and showed lower yields at the end of the seven cycles.
The gradual decrease in decolorization in the subsequent cycles
has been explained differently in the literature. This may be related
with enzyme inactivation. Indeed, upon repeated uses, the blocking
of some pores of beads by substrate or product may take place. This
restriction may cause a decrease in the efficient activity of C. gallica
laccase entrapped into the gel after successive decolorization cycles.
However, Anwar et al. (2009) emphasized that the decrease in activity
occurred on further reusemay be due to the leakage of enzyme
from alginate beads during washing at the end of each cycle.
In the literature, there are several articles reporting the successful
reuse of various immobilized laccase systems. Thus, a laccase
from Panus conchatus immobilized on activated polyvinyl
alcohol retained 60% of its activity after ten batch uses and more
than 50% after 17 batch uses (Yinghui et al., 2002) and a laccase
from P. sanguineus immobilized on copper tetraaminophthalocyanine
(CuTAPc)-Fe3O4 magnetic nano-composite retained
80% of its initial activity after 5 bath uses (Xiao et al., 2006).