Production of a potential liquid plant bio-stimulant by immobilized Piriformospora indica in repeated-batch fermentation process Vassilev, Nikolay Bojkov Eichler-Löbermann, Bettina Flor Peregrín, Elena Martos Núñez, María Vanesa Reyes Requena, Antonia Vassileva, Maria Hristova Biofertilizers Piriformospora indica Immobilization P solubilization Plant growth promotion Piriformospora indica, a mycorrhizal-like fungus able to establish associations with roots of a wide range of plants, supporting plant nutrition and increasing plant resistance and tolerance to stress, was shown to solubilise phosphate applied in the form of animal bone char (HABO) in fermentation systems. The process of P solubilisation was caused most likely by proton extrusion and medium pH lowering. The fungal mycelium was successfully immobilized/retained in a polyurethane foam carrier. Further employment of the immobilized mycelium in repeated-batch fermentation process resulted in at least 5 cycles of P solubilization. The concentration of soluble P increased during the experiment with 1.0 and 3.0 g HABO l−1 and at the end of the 5th batch cycle reached 40.8 and 120 mg l−1, respectively. The resulting final liquid product, without or with solubilized phosphate, was found to significantly increase plant growth and P plant uptake. It can be used as a biostimulant containing microbial plant growth-promoting substances and soluble P derived from renewable sources (HABO) thus supporting the development of sustainable agro-ecosystems. 2018-02-15T11:14:27Z 2018-02-15T11:14:27Z 2017-05-16 journal article Vassilev, N.; et al. Production of a potential liquid plant bio-stimulant by immobilized Piriformospora indica in repeated-batch fermentation process. AMB Express, 7: 106 (2017). [http://hdl.handle.net/10481/49563] 2191-0855 http://hdl.handle.net/10481/49563 10.1186/s13568-017-0408-z eng http://creativecommons.org/licenses/by-nc-nd/3.0/ open access Creative Commons Attribution-NonCommercial-NoDerivs 3.0 License Biomed Central