A pilot plant investigation for bioprocessing has been undertaken to develop a simple, nonaseptic, low-cost single process for production of fungal biomass protein (FBP) and wastewater treatment using starch processing wastewater. It has been confirmed that the newly developed external air-lift bioreactor was very suitable for bioconversion of starch materials and FBP production by the microfungi Aspergillus oryzae and Rhizopus arrhizus. Bioproduct yields of 8.5 g dm(-3) of FBP that contained 46-50% protein were obtained within a comparatively short retention time. A fungal biomass productivity in a range of 0.85-0.92 g dm(-3) h(-1) and removals of total suspended solids and 95% COD were achieved in batch, semi-continuous and continuous processes. The operation modes of the semicontinuous and continuous processes demonstrated a high biological dynamics in fungal biomass productivity and COD reduction. The semi-continuous process appeared to be the most practical mode.