The thermal stability studies on the free and immobilized laccase
were conducted by treating laccase in sodium citrate buffer
solution (pH 4.0) for variable incubation time at 60 C. Samples
were withdrawn every 30 min and were then taken for the activity
measurement immediately. The operating stability of the immobilized
laccase was assessed by performing several consecutive operating
cycles using 0.5 mM ABTS at 25 C. At the end of each cycle,
the immobilized laccase was separated with a magnet, washed
three times with sodium citrate buffer (pH 4.0), and repeated with
a fresh aliquot of substrate, as described by Davis and Burns