Solid-state fermentation optimization for mass production and stability of the nematophagous fungus Purpureocillium lilacinum

Crop infestation by plant-parasitic nematodes is a persistent problem in greenhouse and open-field horticultural systems. Purpureocillium lilacinum strains SR14 and SR38 have demonstrated biocontrol potential against Nacobbus aberrans s.l. In this study, conidia production by solid-state fermentation (SSF) was evaluated with the aim of developing an effective biocontrol product against this nematode. Rice (R) was identified as the most suitable substrate for fungal conidial production, outperforming peanut shell (PS), ground peanut shell (GPS), and their mixtures with rice (PS+R and GPS+R, 1:1). Optimal fermentation conditions varied between strains: SR14 achieved maximum conidial yield, as well as the highest conidial viability and germination, on rice in bag containers at 0.99 a W , 20 °C, and 20 days; whereas SR38 showed the best performance on rice in glass jars at 0.98 a W , 24 °C, and 10 days. Conidia produced under these conditions exhibited high pathogenicity (>77% egg parasitism) and produced enzymes, including chitinases and proteases. In addition, the formulated biocontrol product maintained high viability (a mean around 1.9×10 10 CFU g -1 , for both strain and conditions) after 240 days (around 8 months) storage at room temperature. Overall, these results suggest that SSF on rice is a promising strategy for the production of P. lilacinum conidia , providing a foundation for future scale-up and validation studies.