Optimization of solid-state fermentation parameters and post-harvest stabilization for the mass production of <i>Trichoderma citrinoviride</i> EGE-K-128 micropropagules

In this study, solid-state fermentation (SSF) parameters were optimized for micropropagule production of <i>Trichoderma citrinoviride</i> EGE-K-128, a strain with microbial fertilizer potential. Unlike previous studies primarily focused on biomass production, this work combines process optimization, mechanical fragmentation for propagule recovery, and post-production stabilization within a single framework. Among the tested nitrogen sources, 3% malt sprout resulted in the highest micropropagule yield and was selected as the optimum nitrogen source. Optimal Erlenmeyer-scale conditions were determined as 70% initial moisture content, an inoculum density of 1.0 × 10⁸ spores/mL, an incubation temperature of 30 °C, and 180 s post-production homogenization, yielding up to 2.1 × 10¹⁰ micropropagules/g. In tray-type SSF systems, 144.2 g substrate provided improved specific yield and scale-up suitability. During oven drying, 9% glycerol at 40 °C ensured the highest post-drying viability, reaching 1.1 × 10¹⁰ micropropagules/g. In freeze-drying experiments, the combination of 5% trehalose and 10% skim milk with freezing at -20 °C yielded significantly higher viability (3.0 × 10⁹ micropropagules/g) compared to -80 °C (6.8 × 10⁸ micropropagules/g). Overall, this study defines efficient production and stabilization conditions for <i>T. citrinoviride</i> micropropagules.