Biosolubilization of Mineral Insoluble phosphates by Immobilized Fungi (Aspergillus Niger) in Fluidized Bed Bioreactor

Abstract

Phosphorus (P) is one of the most essential macronutrients required for the growth of plants and is added to soil in the form of phosphatic fertilizers. However, because of mineral re-precipitation, large amount of applied phosphate fertilizer may become unavailable to the plant. The ability of soil microorganisms to transform insoluble forms of phosphorus to an accessible form is an important path in plant growth-promoting for increasing plant yields. In this study, Aspergillus Niger, a fungal strain isolated from agricultural soil samples, was tested for its ability to solubilize different phosphated matrixes (TCP, DCP, phosphates rock). The isolated fungus exhibits high capacities to solubilize all tested phosphates. The solubilization of insoluble phosphates was associated with a drop in the pH of the culture medium. The fungal biomass was entrapped in alginate and polyacrylamide gels and was used for solubilizing mineral phosphates in fluidized bed bioreactor. The highest specific solubilization rates were obtained when A. Niger was entrapped in alginate beads. The use of the bioreactor in consecutive cycles of solubilization showed the interest of the biomass immobilization in the stability of the bioreactor. Immobilized cells in alginate continuously solubilize phosphate even after 5 cycles of solubilization without loss of activity. The phosphorus biosolubilization performances of isolated strains may open new possibilities for their biotechnology application and allow the use of this fungus in the soil fertilization.

Quantitative and qualitative estimation of Moroccan Trichoderma isolates capacity to solubilize rock phosphate

“…In addition, the studies of Rawat and Tewari (2011) and Promwee et al (2014) reported that Trichoderma species showed good mycelial growth, but no formation of a halo-zone on the solid medium containing an insoluble inorganic phosphorus source. In contrast, the Zeroual et al (2012) study has revealed that Aspergillus niger was able to form the halo-zone on the agar plate.…”

“…In addition, in natural habitats, some phytopathogenic fungi such as Pythium and Rhizoctonia have been shown to be incapable of solubilizing phosphates and can be easily suppressed by the high competitive efficiency of T. harzianum by P absorption (Altomare et al, 1999). While other fungi, case of Aspergillus niger, have shown a high performance to solubilize different sources of phosphate (Zeroual et al, 2012). The solubilization of phosphates by Trichoderma species has been reported in several studies (Akintokun et al, 2007;Saravanakumar et al, 2013).…”

Aislamiento y selección de hongos de suelo solubilizadores de fósforo nativos del estado de Coahuila, México

“…A la fecha, la mayoría de los estudios sobre hongos solubilizadores in vitro se han desarrollado con diversas cepas de Aspergillus niger (Vassilev et al, 1996;Narsian y Patel., 2000;Singh et al, 2011Ashok et al, 2012Zeroual et al, 2012). Numerosos trabajos (Mesa Garriga et al, 2005;Velásquez et al, 2010;Paredes-Mendoza y Espinosa-Victoria, 2010;Leal et al, 2011;Pérez et al, 2012) evidencian que A. niger produce una gran cantidad de ácidos orgánicos tales como ácido cítrico, láctico, málico, oxálico o tartárico (Paredes-Mendoza y Espinosa-Victoria, 2010; Pérez et al, 2012).…”