Olive mill wastewater (OMW) usually has to be diluted before biological treatment. In the present work seven strains of Penicillium
isolated from OMW disposal ponds were tested for biomass production and biodegradation of undiluted OMW. Best results
were obtained by using strain P4, which formed 21.50 g (dry weight) of biomass per litre of undiluted wastewater after 20 days of
cultivation. This and other strains also carried out an outstanding reduction of the chemical oxygen demand (COD) and the
phenolic content of OMW, as well as a pH raise. The process could be accelerated by agitation. OMW fermented with Penicillium P4
was devoid of its initial antibacterial activity against Bacillus megaterium ATCC 25848. Ó 2000 Elsevier Science Ltd. All rights
reserved.