Three strains of filamentous fungi (A. oryzae 448, A. niger 334, and R. oligosporus 2710) were used for the biodegradation of highly loaded wastewater from the potato industry. The wastewater was o obtained in a protein recovery unit from potato juice water (deproteinized wastewater). The wastewater treatment process was carried out 48 and 72 h in a Biostat B laboratory fermentor the working volume of which was 1.5 l. During the 72h process, the A. oryzae 448 strain caused the COD to decrease by 70 %. The A. niger and R. oligosporus strains used to treat the wastewater caused the COD level to similarly decrease, i.e. by 58 % and 52 %, respectively. The application of the selected moulds to the biodegradation of potato wastewater resulted in a very high reduction of biogenic substances. In the case of total phosphorus, cultivating the R. oligosporus 2710 strain for 48 h proved beneficial; during this period, the amount of this element in wastewater was reduced by 82 %. Then again, the amount of the nitrogen compounds was reduced by 83 % during the 72h biodegradation process with the use of the A. oryzae 448 strain. Regardless of the type of mould tested, the highest amount of mould biomass was produced during the 48h fermentation process. The A. niger 334 strain proved to have the highest biomass productivity (13.2 g d.m. / l of wastewater). The biomass produced was characterized by a high content of protein (42 – 44 %) and a high feed energy value.