Production of Conidia by the Fungus Metarhizium anisopliae Using Solid-State Fermentation

Abstract

This chapter describes the production of conidia by Metarhizium anisopliae using solid-state fermentation. Before production of conidia, procedures for strains conservation, reactivation, and propagation are essential in order to provide genetic stability of the strains. The strain is conserved in freeze-dried vials and then reactivated through insect inoculation. Rice is used as a substrate for the conidia production in two different bioreactors: plastic bags and tubular bioreactor. The CO₂ production in the tubular bioreactors is measured with a respirometer; this system allows calculating indirect growth parameters as lag time (t_lag) (25–35 h), maximum rate of CO₂ production (rCO_{2 max}) (0.5–0.7 mg/gdm h), specific rate of CO₂ production (μ) (0.10–0.15 1/h), and final CO₂ production (CO₂) (100–120 mg/gdm). Conidial yield per gram of dry substrate (gdm) should be above 1 × 10⁹ conidia/gdm after 10 days of incubation. Germination and viability of conidia obtained after 10 days of incubation should be above 80 % and 75 %, respectively. Bioassays using of Tenebrio molitor as a host insect should yield a final mortality above 80 %.