Industrial wastewaters and dewatered sludge: rich nutrient source for production and formulation of biocontrol agent, Trichoderma viride

Axenic cultivation of biocontrol fungus Trichoderma viride was conducted on a synthetic medium and different wastewaters and wastewater sludges in shake flasks to search for a suitable raw material resulting in higher biocontrol activity. Soluble starch based synthetic medium, dewatered municipal sludge, cheese industry wastewater sludge, pre-treated and untreated pulp and paper industry wastewater and slaughter house wastewater (SHW) were tested for T. viride conidia and protease enzyme production. The maximum conidia production followed the order, soluble starch medium (>109 c.f.u./mL), untreated pulp and paper industry wastewater (4.9 × 107 c.f.u./mL) > cheese industry wastewater (1.88 × 107 c.f.u./mL) ≈ SHW (1.63 × 107 c.f.u./mL) > dewatered municipal sludge (3.5 × 106 c.f.u./mL) > pre-treated pulp and paper industry wastewater (1.55 × 106 c.f.u./mL). The protease activity of T. viride was particularly higher in slaughterhouse wastewater (2.14 IU/mL) and dewatered municipal sludge (1.94 IU/mL). The entomotoxicity of soluble starch based synthetic medium was lower (≈6090 SBU/μL) in contrast to other raw materials. The entomotoxicity inversely decreased with carbon to nitrogen ratio in the growth medium and the conidia concentration and protease activity also contributed to the entomotoxicity. The residual c.f.u./g formulation of T. viride conidia were up to approximately, 90% after 1 month at 4 ± 1 °C and about 70% after 6 months at 25 ± 1 °C. Thus, production of T. viride conidia would help in marketability of low cost biopesticide from the sludge and safe reduction of pollution load.