Evaluation of inert and organic carriers for Verticillium lecanii spore production in solid-state fermentation

Growth and sporulation of Verticillium lecanii on inert and organic carriers (sugar-cane bagasse, corncob, rice straw, polyurethane foam and activated carbon) in a solid-state fermentation process was studied. Sugar-cane bagasse and polyurethane foam produced 10(10) spores g(-1) dry carrier whereas corncob, rice straw, and activated carbon yielded, respectively 8 × 10(9), 4 × 10(9), and 3 × 10(8) spores g(-1). Chitinase activity of the conidia was in the following order: sugar-cane bagasse (3.3 U mg(-1)) > wheat bran (3.0 U mg(-1)) > polyurethane foam (2.7 U mg(-1)). There was no significant difference (2.5-2.7 U mg(-1)) in the proteinase activity among the conidia from the three cultures. Scanning electron microscopy shows that aerial mycelium freely penetrated into the internal area of polyurethane foam. Sugar-cane bagasse provided enough area for vegetative hyphae to attach. Of the carriers analyzed, polyurethane foams and sugar-cane bagasse were the best carriers for V. lecanii growth and spore production.