Solid-state fermentation of paper sludge to obtain spores of the fungus Trichoderma asperellum

Paper production generates large quantities of a solid waste known as papermaking sludge (PS), which needs to be handled properly for final disposal. The high amount of this byproduct creates expensive economical costs and induces environmental and ecological risks. Therefore, it is necessary to search uses for PS, in order to reduce the negative environmental impact and to generate a more valuable byproduct. Due to the cellulolytic composition of PS, this work evaluated a solid state fermentation process using it as substrate to obtain spores of the fungus Trichoderma asperellum. Optimal conditions to obtain T. asperellum spores were: 60% water content, 3% (w/w) salts (Nutrisol P^® and Nutrisol K^®), inoculum concentration at 1x10⁵ spores/g, and pasteurized or sterilized PS. Under these conditions it was possible to obtain 2.37x10⁹ spores/g. T. asperellum spores applied directly to pepper (Capsicum anuum) seeds without PS increased significantly seedling dry mass in greenhouse assays. This work suggests an alternative, economic and abundant substrate for production of T. asperellum spores.