title: Medium pH, carbon and nitrogen concentrations modulate the phosphate solubilization efficiency of Penicillium purpurogenum through organic acid production.
abstract: OBJECTIVE
  To study phosphate solubilization in Penicillium purpurogenum as function of medium pH, and carbon and nitrogen concentrations.
  
  
  RESULTS
  Tricalcium phosphate (CP) solubilization efficiency of P. purpurogenum was evaluated at acid or alkaline pH using different C and N sources. Glucose- and (NH(4) )(2) SO(4) -based media showed the highest P solubilization values followed by fructose. P. purpurogenum solubilizing ability was higher in cultures grown at pH 6·5 than cultures at pH 8·5. Organic acids were detected in both alkaline and neutral media, but the relative percentages of each organic acid differed. Highest P release coincided with the highest organic acids production peak, especially gluconic acid. When P. purpurogenum grew in alkaline media, the nature and concentration of organic acids changed at different N and C concentrations. A factorial categorical experimental design showed that the highest P-solubilizing activity, coinciding with the highest organic acid production, corresponded to the highest C concentration and lowest N concentration.
  
  
  CONCLUSIONS
  The results described in the present study show that medium pH and carbon and nitrogen concentrations modulate the P solubilization efficiency of P. purpurogenum through the production of organic acids and particularly that of gluconic acid. In the P solubilization optimization studies, glucose and (NH(4) )(2) SO(4) as C and N sources allowed a higher solubilization efficiency at high pH.
  
  
  CONCLUSIONS
  This organism is a potentially proficient soil inoculant, especially in P-poor alkaline soils where other P solubilizers fail to release soluble P. Further work is necessary to elucidate whether these results can be extrapolated to natural soil ecosystems, where different pH values are present. Penicillium purpurogenum could be used to develop a bioprocess for the manufacture of phosphatic fertilizer with phosphate calcium minerals.
authors.affiliation: Dpto de Química Biológìca, Universidad de Buenos Aires, Buenos Aires, Argentina. scervino@bg.fcen.uba.ar
authors.forename: J M
authors.initials: JM
authors.lastname: Scervino
authors.forename: V L
authors.initials: VL
authors.lastname: Papinutti
authors.forename: M S
authors.initials: MS
authors.lastname: Godoy
authors.forename: M A
authors.initials: MA
authors.lastname: Rodriguez
authors.forename: I
authors.initials: I
authors.lastname: Della Monica
authors.forename: M
authors.initials: M
authors.lastname: Recchi
authors.forename: M J
authors.initials: MJ
authors.lastname: Pettinari
authors.forename: A M
authors.initials: AM
authors.lastname: Godeas
mesh_terms: D002130:Calcium Phosphates / Q000378:metabolism*; D002244:Carbon / Q000378:metabolism*; D003470:Culture Media; D005942:Gluconates / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D009584:Nitrogen / Q000378:metabolism*; D010407:Penicillium / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism*; D012988:Soil Microbiology; D012995:Solubility
chemical_list: D002130:Calcium Phosphates; D003470:Culture Media; D005942:Gluconates; D002244:Carbon; C018392:tricalcium phosphate; D009584:Nitrogen; C030691:gluconic acid