Conidiation and lytic enzyme production by Trichoderma viride at different solids concentration of pre-treated municipal wastewater sludge was examined in a 15-L fermenter. The maximum conidia concentration (5.94 x 10(7) CFU mL(-1) at 96 h) was obtained at 30 g L-1 suspended solids. The maximum lytic enzyme activities were achieved around 12-30 h of fermentation. Bioassay against a fungal phytopathogen, Fusarium sp. showed maximum activity in the sample drawn around 96 h of fermentation at 30 g L-1 suspended solids concentration. Entornotoxicity against spruce budworm larvae showed maximum value approximate to 17290 SBU mu L-1 at 30 g L-1 suspended solids concentration at the end of fermentation (96 h). Plant bioassay showed dual action of T viride, i.e., disease prevention and growth promotion. The rheological analyses of fermentation sludges showed the pseudoplastic behaviour. In order to maintain required dissolved oxygen concentration >= 30%, the agitation and aeration requirements significantly increased at 35 g L-1 compared to 30 and 25 g L-1. The oxygen uptake rate and volumetric oxygen mass transfer coefficient, kLa at 35 g L-1 did not increase in comparison to 30 g L-1 due to theological complexity of the broth during fermentation. Thus, the successful fermentation operation of the biocontrol fungus T viride is a rational indication of its potential for mass-scale production for agriculture and forest sector as a biocontrol agent. (C) 2007 Elsevier Inc. All rights reserved.