Solubilization of animal bonechar by a filamentous fungus employed in solid state fermentation

Experts are concerned by the scarcity of rock phosphate and the vulnerability of the modern agricultural systems which is highly dependent on the existing fertilizer industry based exclusively of this natural, finite, non-renewable resource. In this work, the filamentous fungus Aspergillus terreus, which produce itaconic acid, was used to solubilize animal bonechar (HABO, a derivate from meat industry) in conditions of solid-state fermentation. By-products of the sugar and olive oil production industry (sugar beet press-mud and dry olive residues) containing lignocellulosic mass were used as substrates. The effect of humidity, inoculum size, nitrogen source, and phosphate on itaconic acid production and HABO solubilization was studied at optimal other conditions. Results showed that 70% humidity, 1.5 g meat and bone meal, 1 ml initial inoculum size, and 20 g HABO kg(-1) dry substrate remarkably enhanced the itaconic acid production which reached 44.0 g/kg dry substrate. At these conditions, the amount of soluble P in the medium reached 30.9 mg/flask which corresponded to 50% yield of soluble P vs. total P in the supplied insoluble phosphate. Glycerol was applied in the medium for inoculum production and further in the solid-state fermentation process it was introduced as a part of the medium and as a moistening agent. The results reported here should be evaluated bearing in mind the problem of phosphate fertilizers, P plant nutrition, and existing phosphate bearing resources. On the other hand, due to the fact that solid (waste) particles serve simultaneously as a support and source of nutrients for cell growth, this laboratory scheme can be used in processes of production and formulation of soil microbial inoculants. (C) 2013 Elsevier B.V. All rights reserved.