P. ostreatus Peroxidase Profiles 415 Applied Biochemistry and Biotechnology Vol. 102–103, 2002 415 *Author to whom all correspondence and reprint requests should be addressed. Copyright © 2002 by Humana Press Inc. All rights of any nature whatsoever reserved. 0273-2289/02/102–103/0415/$13.75 Mn 2+ Alters Peroxidase Profiles and Lignin Degradation by the White-Rot Fungus Pleurotus ostreatus Under Different Nutritional and Growth Conditions RONI COHEN, LIMOR PERSKY, ZAHIT HAZAN-EITAN, ODED YARDEN, AND YITZHAK HADAR* Department of Plant Pathology and Microbiology and The Otto Warburg Center for Biotechnology in Agriculture, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, PO Box 12, Rehovot 76100, Israel, E-mail: hadar@agri.huji.ac.il Abstract The white-rot fungus Pleurotus ostreatus produces two types of extracellu- lar peroxidases: manganese-dependent peroxidase (MnP) and versatile per- oxidase (VP). The effect of Mn 2+ on fungal growth, peroxidase activity profiles, and lignin degradation by P. ostreatus was studied in liquid culture and under solid-state fermentation conditions on perlite, the latter resem- bling the natural growth conditions of this fungus. The fungus was grown in either a defined asparagine-containing basidiomycete selective medium (BSM) or in a rich peptone medium (PM). Biomass production, as deter- mined by respiration experiments in solid-state fermentation and liquid cultures and fungal growth on Petri dishes, was higher in the PM than in the BSM. Mn 2+ affected biomass production only in the PM on Petri dishes. In the nonamended PM, high levels of MnP and VP activity were detected relative to the nonamended BSM. Nevertheless, a higher rate of 14 C-lignin mineralization was measured in the Mn 2+ -amended BSM, as determined during the course of 47 d of fermentation. Mn 2+ amendment of the PM increased mineralization rate to that obtained in the Mn 2+ -amended BSM. The enzyme activity profiles of MnP and VP were studied in the BSM using anion-exchange chromatography. In the nonamended BSM, only minute levels of MnP and VP were detected. On Mn 2+ amendment, two MnP isoen- zymes (B1 and B2) appeared. Isoenzyme B2 was purified and showed 100% identity with the MnP isoenzyme purified in our previous study from PM-solid-state fermentation (P6). P6 was found to be the dominant isoenzyme