Biodegradation of crystal violet by white rot fungus Pleurotus ostreatus BP in rice straw solid-state medium mostly depended on low molecular mass fraction (LMMF) and the hypothetical metabolic pathways of crystal violet by LMMF was proposed by the biodegradation of crystal violet and by the deduced six metabolites formed. (C) 2009, The Society for Biotechnology, Japan. All rights reserved.