Animal bone char solubilization with itaconic acid produced by free and immobilized Aspergillus terreus grown on...

Cells of Aspergillus terreus, free and immobilized in polyurethane foam, were employed in itaconic acid fermentation processes on glycerol-based media. The purpose was to assess their suitability for animal bone char solubilization and the development of a biotechnological alternative to P fertilizers chemically produced from rock phosphate. Animal bones constitute a renewable source of P that can replace the traditionally used finite, nonrenewable rock phosphate as a P source. Glycerol was an excellent substrate for growth (10.2 g biomass L(-1)) and itaconic acid production (26.9 g L(-1)) by free fungal cells after 120-h fermentation. Simultaneously, A. terreus solubilized the insoluble phosphate to a yield of 23 to 50 %, depending on the particle size and concentration. Polyurethane foam cut into cubes of 0.5-0.6 cm per side, with 0.3 mm pore size and applied at 2.0 g L(-1) proved to be an excellent cell carrier. In repeated batch fermentation, the immobilized mycelium showed a high capacity to solubilize animal bone char, which resulted on average in 168.8 mg L(-1) soluble phosphate per 48-h cycle and 59.4 % yield (percent of total phosphate) registered in the fourth batch.