Preparation and characterization of cross-linked laccase aggregates and their application to the elimination of endocrine disrupting chemicals

Laccase from the white rot fungus Coriolopsis polyzona was immobilized for the first time through the formation of cross-linked enzyme aggregates (CLEAs). Laccase CLEAs were produced by using 1000 g of polyethylene glycol per liter of enzyme solution as precipitant and 200 mu M of glutaraldehyde as a cross-linking agent. These CLEAs had a laccase activity of 148 U g(-1) and an activity recovery of 60.2% when using 2,2 '-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) as substrate. CLEAs formed by co-aggregation with bovine serum albumin (BSA) as a stabilizer showed lower laccase activity and affinity for ABTS than those without BSA. The CLEAs co-aggregated with BSA showed higher residual activity against a protease, NaN3, EDTA, methanol and acetone. The thermoresistance was higher for CLEAs than for free laccase and also higher for CLEAs co-aggregated with BSA than for simple CLEAs when tested at a pH of 3 and a temperature of 40 degrees C. Finally, laccase CLEAs were tested for their capacity to eliminate the known or suspected endocrine disrupting chemicals (EDCs) nonylphenol, bisphenol A and triclosan in a fluidized bed reactor. A 100-ml reactor with 0.5 mg of laccase CLEAs operated continuously at a hydraulic retention time of 150 min at room temperature and pH 5 could remove all three EDCs from a 5 mg l(-1) solution. (C) 2007 Elsevier B.V. All rights reserved.