using two different wastes, coupled with concentration and virulence tests of the produced conidia against the
pest Tenebrio molitor. Beauveria bassiana CECT 20374 was used in solid state fermentation (SSF) operating under
batch strategy. Two substrates with different biodegradability (rice husk and beer draff) were tested, successfully
scaling from 1.5 L to 22 L bioreactors. Higher conidia production was reached using beer draff as substrate (2.5
× 109 and 6.0 × 108 conidia g􀀀 1 dry matter in 1.5 and 22 L reactors respectively) highlighting air free porosity
relevance as scale-up parameter. Concentration and dose-response tests against larvae and adult Tenebrio molitor
were performed to compare strain CECT 20374 with control strain KVL 13–39 (a B. bassiana strain previously
tested against T. molitor). Virulence effect of the 22 L fermentation product of strain CECT using rice husk or beer
draff was tested against T. molitor adult stage. However, quality loses between conidia produced in agar plates
and fermented products were observed (from 75 to 80% mortality in plates to 40% in rice husk and 50–60% in
beer draff fermented products respectively). The differences between plate and fermented samples also indicated
fermentation process, extraction and conservation steps as possible causes for quality losses, highlighting the
need to optimize them to maximize virulence maintenance.