Abstract
An alkalophilic and halotolerant laccase from γ-proteobacterium JB catalyzed in high concentrations of organic solvents and various salts. The enzyme retained 80-100% activity in 10% concentration of dimethylsulfoxide (DMSO), ethanol, acetone or methanol; 100, 85 and 50% activity in 20 mM MgCl2, 5.0 mM MnCl2 and 0.1 mM CuCl2; 140, 120 and 110% activity in 5.0 mM MnSO4, 10 mM MgSO4 and 1mM CaSO4, respectively. Sodium halides inhibited the enzyme in the order: F-> Br-> I-> Cl-. In 0.5 M NaCl, pH 6.0, laccase was ~60% active. Decolorization of indigo carmine by laccase at pH 9.0 was not inhibited even in the presence of 0.5 M NaCl. Release of chromophoric, reducing and hydrophobic compounds during biobleaching of straw rich-soda pulp by laccase was not inhibited when the enzyme was applied in the presence of 1 M NaCl at pH 8.0. Laccase retained 50% residual activity even when incubated with 5% calcium hypochlorite for 30 min.
