The potential use of aqueous two-phase systems (ATPS) to establish a viable protocol for the recovery of laccase from the residual compost of Agaricus bisporus was evaluated. The evaluation of system parameters Such as poly (ethylene glycol) (PEG) molecular mass, concentration of PEG as well as salt and system pH was carried out to determine under which conditions the laccase concentrates predominantly to the top PEG-rich phase. PEG 1000-phosphate ATPS proved to be suitable for the primary recovery of laccase. Art extraction ATPS stage comprising volume ratio equal to 1.0, PEG 1000 18.2% (w/w), phosphate 15.0% (w/w), system pH of 7.0 and loaded with 5% (w/w) of crude extract from residual compost allowed the laccase recovery. The use of ATPS resulted in one-single primary recovery stage process that produced an overall yield of 95%. The results reported here demonstrated the potential application of ATPS for the valorisation of residual material and the potential establishment of a downstream process to obtain value added products with commercial application. (C) 2008 Elsevier Ltd. All rights reserved.