Cross-linked enzyme aggregates of Cerrena laccase: Preparation, enhanced NaCl tolerance and decolorization of Remazol Brilliant Blue Reactive

• Cross-linked enzyme aggregates were prepared for Cerrena laccase.
• Laccase CLEAs showed improved tolerance to NaCl, metal ions and organic solvents.
• NaCl was a mixed-type inhibitor of both free and immobilized laccases.
• CLEAs had higher inhibition constants KI and KIS than free laccase.
• CLEAs showed less inhibition by NaCl in RBBR decolorization than free laccase.

White-rot fungus Cerrena sp. strain HYB07 produces laccase with high yields and strong decolorization ability. Cerrena laccase was immobilized by preparing cross-linked enzyme aggregates (CLEAs), and ammonium sulfate and glutaraldehyde were the optimal precipitant and cross-linking agent, respectively. An activity recovery rate of 68.1% was obtained at pH 8 after precipitation with (NH4)2SO4 and cross-linking with 30 mM glutaraldehyde for 3 h at 25 ºC. Immobilized Cerrena laccase demonstrated improved tolerance to NaCl, metal ions and organic solvents. NaCl was a mixed-type inhibitor of both free and immobilized laccases with 2, 2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) as the substrate, and the improvement of NaCl resistance by laccase immobilization was quantified kinetically. Laccase CLEAs had higher inhibition constants KI and KIS compared to free laccase, suggesting that the affinity of NaCl to laccase was attenuated by immobilization. Laccase CLEAs also displayed greater velocity and efficiency in Remazol Brilliant Blue Reactive decolorization in the presence of NaCl than free laccase. Greater differences in the half time (t1/2) of Remazol Brilliant Blue Reactive decolorization by free and immobilized laccases were observed with increasing NaCl concentrations.

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