Biopesticide Production from Trichoderma harzianum by Solid-State Fermentation: Impact of Drying Process on Spore Viability

Among the sustainable agricultural approaches, biological control agents are a promising new alternative to agrochemicals. However, expensive production methods, formulation, poor storage stability and short shelf life are limiting their adoption. One of the promising options for biopesticide production is solid-state fermentation (SSF). This study was conducted to evaluate spore production by two Trichoderma harzianum, Rey 3 and TF2, under forced air drying in SSF. A mixture of agroindustrial byproducts (sugarcane bagasse, vine shoots, wheat bran, potato flour and chitin) were used as substrates. CO2 generated during fungi growth was recorded by respirometry. We also investigated the effect of hydric stress conditions on the decreasing phase of Trichoderma metabolism as an inducer of sporulation. In parallel, we analyzed the viability of T. harzianum TF2 and spores under different storage conditions (lyophilized, frozen and dried). Under the present culture conditions, the highest production of spores was 10.1 ± 0.3 × 109 spores/g DM (Dry Material) at 52 h for T. harzianum Rey 3 and 8.9 ± 0.6 × 109 spores/g DM at 72 h for T. harzianum TF2. The forced dry air during the fermentation process had no notable effect on spore production, but it did increase the spore viability (29% viability for T. harzianum Rey 3 and 33% viability for T. harzianum TF2). In parallel, the chitinase, cellulase, xylanase and lipase activities were evaluated, obtaining interesting results regarding enzymatic activities.